Cell Membrane Structure and Function
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Membranes and Cell Transport • All cells are surrounded
by a plasma membrane. • Cell membranes are composed of a lipid bilayer with globular proteins embedded in the bilayer. • On the external surface, carbohydrate groups join with lipids to form glycolipids, and with proteins to form glycoproteins. These function as cell identity markers.
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Fluid Mosaic Model • In 1972, S. Singer and G. Nicolson proposed the Fluid
Mosaic Model of membrane structure Glycoprotein
Extracellular fluid
Glycolipid
Carbohydrate
Cholesterol Transmembrane proteins Peripheral protein
Cytoplasm Filaments of cytoskeleton
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Phospholipids •
•
In phospholipids, two of the –OH groups on glycerol are joined to fatty acids. The third –OH joins to a phosphate group which joins, in turn, to another polar group of atoms. The phosphate and polar groups are hydrophilic (polar head) while the hydrocarbon chains of the 2 fatty acids are hydrophobic (nonpolar tails).
Choline Phosphate Glycerol
Fatty acids Hydrophilic head Hydrophobic tails Structural formula
Space-filling model
Phospholipid symbol
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Phospholipids • Glycerol
• Two fatty acids • Phosphate group
Hydrophilic heads
ECF WATER
Hydrophobic tails
ICF WATER
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Phospholipid Bilayer • Mainly 2 layers of phospholipids; the non-polar tails
point inward and the polar heads are on the surface. • Contains cholesterol in animal cells. • Is fluid, allowing proteins to move around within the bilayer. Polar hydro-philic heads Nonpolar hydro-phobic tails
Polar hydro-philic heads
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The Fluidity of Membranes • • •
•
Membrane molecules are held in place by relatively weak hydrophobic interactions. Most of the lipids and some proteins drift laterally in the plane of the membrane, but rarely flip-flop from one phospholipid layer to the other. Membrane fluidity is influenced by temperature. As temperatures cool, membranes switch from a fluid state to a solid state as the phospholipids pack more closely. Membrane fluidity is also influenced by its components. Membranes rich in unsaturated fatty acids are more fluid that those dominated by saturated fatty acids because the kinks in the unsaturated fatty acid tails at the locations of the double bonds prevent tight packing.
Lateral movement (~107 times per second)
Flip-flop (~ once per month)
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Membrane Components •
Steroid Cholesterol • • • •
Wedged between phospholipid molecules in the plasma membrane of animal cells. At warm temperatures (such as 37°C), cholesterol restrains the movement of phospholipids and reduces fluidity. At cool temperatures, it maintains fluidity by preventing tight packing. Thus, cholesterol acts as a “temperature buffer” for the membrane, resisting changes in membrane fluidity as temperature changes.
Cholesterol
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Membrane Components •
Membrane carbohydrates • •
•
Interact with the surface molecules of other cells, facilitating cell-cell recognition Cell-cell recognition is a cell’s ability to distinguish one type of neighboring cell from another
Membrane Proteins • • • •
A membrane is a collage of different proteins embedded in the fluid matrix of the lipid bilayer Peripheral proteins are appendages loosely bound to the surface of the membrane Integral proteins penetrate the hydrophobic core of the lipid bilayer Many are transmembrane proteins, completely spanning the membrane
Fibers of extracellular matrix (ECM)
EXTRACELLULAR SIDE N-terminus
Glycoprotein Carbohydrate
Glycolipid
Microfilaments of cytoskeleton Cholesterol
Peripheral protein
C-terminus
Integral protein
CYTOPLASMIC α Helix
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Functions of Cell Membranes • Regulate the passage of substance into
and out of cells and between cell organelles and cytosol • Detect chemical messengers arriving at the surface • Link adjacent cells together by membrane junctions • Anchor cells to the extracellular matrix
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6 Major Functions Of Membrane Proteins 1. Transport. (left) A protein that spans the membrane may provide a hydrophilic channel across the membrane that is selective for a particular solute. (right) Other transport proteins shuttle a substance from one side to the other by changing shape. Some of these proteins hydrolyze ATP as an energy ssource to actively pump substances across the membrane
2. Enzymatic activity. A protein built into the membrane may be an enzyme with its active site exposed to substances in the adjacent solution. In some cases, several enzymes in a membrane are organized as a team that carries out sequential steps of a metabolic pathway. 3.
ATP Enzymes
Signal transduction. A membrane protein may have a binding site with a specific shape that fits the shape of a chemical messenger, such as a hormone. The external messenger (signal) may cause a conformational change in the protein (receptor) that relays the message to the inside of the cell.
Signal
Receptor
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6 Major Functions Of Membrane Proteins 4.
Cell-cell recognition. Some glyco-proteins serve as identification tags that are specifically recognized by other cells. Glycoprotein
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Intercellular joining. Membrane proteins of adjacent cells may hook together in various kinds of junctions, such as gap junctions or tight junctions
6. Attachment to the cytoskeleton and extracellular matrix (ECM). Microfilaments or other elements of the cytoskeleton may be bonded to membrane proteins, a function that helps maintain cell shape and stabilizes the location of certain membrane proteins. Proteins that adhere to the ECM can coordinate extracellular and intracellular changes
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Functions of Plasma Membrane Proteins Outside
Plasma membrane Inside Transporter
Enzyme
Cell surface identity marker
Cell adhesion
Cell surface receptor
Attachment to the cytoskeleton
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Membrane Transport • The plasma membrane is the boundary that
separates the living cell from its nonliving surroundings • In order to survive, A cell must exchange materials with its surroundings, a process controlled by the plasma membrane • Materials must enter and leave the cell through the plasma membrane. • Membrane structure results in selective permeability, it allows some substances to cross it more easily than others 14
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Membrane Transport • The plasma membrane exhibits selective
permeability - It allows some substances to cross it more easily than others
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Passive Transport • Passive transport is diffusion of a
substance across a membrane with no energy investment • 4 types • Simple diffusion • Dialysis • Osmosis
• Facilitated diffusion
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Kinetic Theory of Matter • All atoms and molecules are in constant
random motion. (Energy of motion is called kinetic energy.) • The higher the temperature, the faster the atoms and molecules move. • We detect this motion as heat. • All motion theoretically stops at absolute zero.
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Solutions and Transport • Solution – homogeneous mixture of two or
more components • Solvent – dissolving medium • Solutes – components in smaller quantities
within a solution • Intracellular fluid – nucleoplasm and
cytosol • Extracellular fluid • Interstitial fluid – fluid on the exterior of the
cell within tissues • Plasma – fluid component of blood 18
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Diffusion •
• •
The net movement of a substance from an area of higher concentration to an area of lower concentration - down a concentration gradient Caused by the constant random motion of all atoms and molecules Movement of individual atoms & molecules is random, but each substance moves down its own concentration gradient.
Lump of sugar
Random movement leads to net movement down a concentration gradient
Water No net movement at equilibrium
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Diffusion Across a Membrane • •
•
The membrane has pores large enough for the molecules to pass through. Random movement of the molecules will cause some to pass through the pores; this will happen more often on the side with more molecules. The dye diffuses from where it is more concentrated to where it is less concentrated This leads to a dynamic equilibrium: The solute molecules continue to cross the membrane, but at equal rates in both directions.
Net diffusion
Net diffusion
Equilibrium
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Diffusion Across a Membrane • • •
Two different solutes are separated by a membrane that is permeable to both Each solute diffuses down its own concentration gradient. There will be a net diffusion of the purple molecules toward the left, even though the total solute concentration was initially greater on the left side
Net diffusion Net diffusion
Net diffusion
Net diffusion
Equilibrium
Equilibrium
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The Permeability of the Lipid Bilayer • Permeability Factors • Lipid solubility • Size • Charge • Presence of channels and transporters • Hydrophobic molecules are lipid soluble and can
pass through the membrane rapidly • Polar molecules do not cross the membrane rapidly • Transport proteins allow passage of hydrophilic substances across the membrane
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Passive Transport Processes • 3 special types of diffusion
that involve movement of materials across a semipermeable membrane • Dialysis/selective diffusion of solutes • Lipid-soluble materials • Small molecules that can pass through membrane pores unassisted • Facilitated diffusion substances require a protein carrier for passive transport • Osmosis – simple diffusion of water
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Osmosis • Diffusion of the solvent across a semipermeable membrane. • In living systems the solvent is always water, so biologists generally define osmosis as the diffusion of water across a semipermeable membrane: 24
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Osmosis Lower concentration of solute (sugar)
Higher concentration of sugar
Same concentration of sugar
Selectively permeable membrane: sugar molecules cannot pass through pores, but water molecules can
Water molecules cluster around sugar molecules
More free water molecules (higher concentration)
Fewer free water molecules (lower concentration) Osmosis
•
Water moves from an area of higher free water concentration to an area of lower free water concentration
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Osmotic Pressure • Osmotic pressure of a solution is the
pressure needed to keep it in equilibrium with pure H20. • The higher the concentration of solutes in a solution, the higher its osmotic pressure. • Tonicity is the ability of a solution to cause a cell to gain or lose water – based on the concentration of solutes
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Tonicity • If 2 solutions have equal [solutes], they are called
isotonic • If one has a higher [solute], and lower [solvent], is hypertonic • The one with a lower [solute], and higher [solvent], is hypotonic Hypotonic solution
H2O
Lysed
Isotonic solution
Hypertonic solution
H2O
H2O
Normal
H2O
Shriveled
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Facilitated Diffusion •
•
Diffusion of solutes through a semipermeable membrane with the help of special transport proteins i.e. large polar molecules and ions that cannot pass through phospholipid bilayer. Two types of transport proteins can help ions and large polar molecules diffuse through cell membranes: Channel proteins – provide a narrow channel for the substance to pass through. • Carrier proteins – physically bind to the substance on one side of membrane and release it on the other. •
EXTRACELLULAR FLUID
Channel protein CYTOPLASM
Solute
Carrier protein
Solute
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Facilitated Diffusion • Specific – each channel or carrier
transports certain ions or molecules only • Passive – direction of net movement is always down the concentration gradient • Saturates – once all transport proteins are in use, rate of diffusion cannot be increased further
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Active Transport • Uses energy (from ATP) to move a
substance against its natural tendency e.g. up a concentration gradient. • Requires the use of carrier proteins (transport proteins that physically bind to the substance being transported). • 2 types: • Membrane pump (protein-mediated active
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Membrane Pump • A carrier protein uses energy from ATP to
move a substance across a membrane, up its concentration gradient:
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The Sodium-potassium Pump •
One type of active transport system [Na+] high [K+] low
1. Cytoplasmic Na+ binds to the sodium-potassium pump.
Na+
Na+ + NaEXTRACELLULAR
FLUID
[Na+] low Na+ [K+] high CYTOPLASM
2. Na+ binding stimulates phosphorylation by ATP.
Na+ Na+
Na+
Na+
6. K+ is released and Na+ sites are receptive again; the cycle repeats.
ATP
P ADP
3. Phosphorylation causes the protein to change its conformation, expelling Na+ to the outside.
Na+
K+ P
K+
5. Loss of the phosphate restores the protein’s original conformation.
K+
4. Extracellular K+ binds to the protein, triggering release of the Phosphate group.
K+ K+
K+ Pi
P Pi
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Coupled transport • 2 stages: • Carrier protein uses ATP to move a substance across the membrane against its concentration gradient. Storing energy. • Coupled transport protein allows the substance to move down its concentration gradient using the stored energy to move a second substance up its concentration gradient:
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Review: Passive And Active Transport Compared Passive transport. Substances diffuse spontaneously down their concentration gradients, crossing a membrane with no expenditure of energy by the cell. The rate of diffusion can be greatly increased by transport proteins in the membrane.
Active transport. Some transport proteins act as pumps, moving substances across a membrane against their concentration gradients. Energy for this work is usually supplied by ATP.
ATP
Diffusion. Hydrophobic molecules and (at a slow rate) very small uncharged polar molecules can diffuse through the lipid bilayer.
Facilitated diffusion. Many hydrophilic substances diffuse through membranes with the assistance of transport proteins, either channel or carrier proteins.
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Bulk Transport • Allows small particles, or groups of
molecules to enter or leave a cell without actually passing through the membrane. • 2 mechanisms of bulk transport: endocytosis and exocytosis.
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Endocytosis • The plasma membrane envelops small
particles or fluid, then seals on itself to form a vesicle or vacuole which enters the cell: • Phagocytosis • Pinocytosis • Receptor-Mediated Endocytosis -
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Three Types Of Endocytosis PHAGOCYTOSIS In phagocytosis, a cell engulfs a particle by Wrapping pseudopodia around it and packaging it within a membraneenclosed sac large enough to be classified as a vacuole. The particle is digested after the vacuole fuses with a lysosome containing hydrolytic enzymes.
EXTRACELLULAR FLUID
Pseudopodium of amoeba “Food” or other particle
Bacterium Food vacuole
Food vacuole An amoeba engulfing a bacterium via phagocytosis (TEM).
PINOCYTOSIS In pinocytosis, the cell “gulps” droplets of extracellular fluid into tiny vesicles. It is not the fluid itself that is needed by the cell, but the molecules dissolved in the droplet. Because any and all included solutes are taken into the cell, pinocytosis is nonspecific in the substances it transports.
1 µm
CYTOPLASM Pseudopodium
0.5 µm
Plasma membrane
Pinocytosis vesicles forming (arrows) in a cell lining a small blood vessel (TEM).
Vesicle
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Process of Phagocytosis
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Receptor-mediated Endocytosis Coat protein Receptor Receptor-mediated endocytosis enables the cell to acquire bulk quantities of specific substances, even though those substances may not be very concentrated in the extracellular fluid. Embedded in the membrane are proteins with specific receptor sites exposed to the extracellular fluid. The receptor proteins are usually already clustered in regions of the membrane called coated pits, which are lined on their cytoplasmic side by a fuzzy layer of coat proteins. Extracellular substances (ligands) bind to these receptors. When binding occurs, the coated pit forms a vesicle containing the ligand molecules. Notice that there are relatively more bound molecules (purple) inside the vesicle, other molecules (green) are also present. After this ingested material is liberated from the vesicle, the receptors are recycled to the plasma membrane by the same vesicle.
Coated vesicle
Coated pit Ligand Coat protein A coated pit and a coated vesicle formed during receptormediated endocytosis (TEMs).
Plasma membrane 0.25 µm
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Exocytosis • The reverse of endocytosis • During this process, the membrane of a vesicle
fuses with the plasma membrane and its contents are released outside the cell:
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Regulation of Gene Expression
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Control of Gene Expression • Controlling gene expression is often
accomplished by controlling transcription initiation. • Regulatory proteins bind to DNA to
either block or stimulate transcription, depending on how they interact with RNA polymerase. 42
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Control of Gene Expression • Prokaryotic organisms regulate gene
expression in response to their environment. • Eukaryotic cells regulate gene
expression to maintain homeostasis in the organism.
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Regulatory Proteins • Gene expression is often controlled
by regulatory proteins binding to specific DNA sequences. • regulatory proteins gain access to the
bases of DNA at the major groove • regulatory proteins possess DNAbinding motifs
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Regulatory Proteins • DNA-binding motifs are regions of
regulatory proteins which bind to DNA • helix-turn-helix motif • homeodomain motif • zinc finger motif • leucine zipper motif
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Helix-Turn-Helix Motif
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Homeodomain Motif
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Zinc Finger Motif
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Leucine Zipper Motif
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Prokaryotic Regulation • Control of transcription initiation can
be: • positive control – increases
transcription when activators bind DNA • negative control – reduces transcription when repressors bind to DNA regulatory regions called operators
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Prokaryotic Regulation • Prokaryotic cells often respond to
their environment by changes in gene expression. • Genes involved in the same metabolic pathway are organized in operons. • Some operons are induced when the metabolic pathway is needed. • Some operons are repressed when the metabolic pathway is no longer needed. 51
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Prokaryotic Regulation • The lac operon contains genes for
the use of lactose as an energy source. • Regulatory regions of the operon include the CAP binding site, promoter, and the operator. • The coding region contains genes for 3 enzymes: β-galactosidase, permease, and transacetylase 52
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Prokaryotic Regulation • The lac operon is negatively
regulated by a repressor protein: • lac repressor binds to the operator to
block transcription • in the presence of lactose, an inducer molecule binds to the repressor protein • repressor can no longer bind to operator • transcription proceeds
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Prokaryotic Regulation • In the presence of both glucose and
lactose, bacterial cells prefer to use glucose. • Glucose prevents induction of the lac operon. • binding of CAP – cAMP complex to the
CAP binding site is required for induction of the lac operon • high glucose levels cause low cAMP levels 57
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Prokaryotic Regulation • The trp operon encodes genes for
the biosynthesis of tryptophan. • The operon is not expressed when the cell contains sufficient amounts of tryptophan. • The operon is expressed when levels of tryptophan are low.
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Prokaryotic Regulation • The trp operon is negatively regulated
by the trp repressor protein • trp repressor binds to the operator to
block transcription • binding of repressor to the operator requires a corepressor which is tryptophan • low levels of tryptophan prevent the repressor from binding to the operator
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Eukaryotic Regulation • Controlling the expression of
eukaryotic genes requires transcription factors. • general transcription factors are
required for transcription initiation • required for proper binding of RNA polymerase to the DNA
• specific transcription factors increase
transcription in certain cells or in response to signals
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Eukaryotic Transcription • General transcription factors bind to
the promoter region of the gene. • RNA polymerase II then binds to the promoter to begin transcription at the start site (+1). • Enhancers are DNA sequences to which specific transcription factors (activators) bind to increase the rate of transcription. 66
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Eukaryotic Transcription • Coactivators and mediators are
also required for the function of transcription factors. • coactivators and mediators bind to
transcription factors and bind to other parts of the transcription apparatus
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Eukaryotic Chromosome Structure • Eukaryotic DNA is packaged into
chromatin. • Chromatin structure is directly related to the control of gene expression. • Chromatin structure begins with the organization of the DNA into nucleosomes. • Nucleosomes may block RNA polymerase II from gaining access to promoters. 70
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Eukaryotic Chromosome Structure • Methylation (the addition of –CH3) of
DNA or histone proteins is associated with the control of gene expression. • Clusters of methylated cytosine nucleotides bind to a protein that prevents activators from binding to DNA. • Methylated histone proteins are associated with inactive regions of 71
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Posttranscriptional Regulation • Control of gene expression usually
involves the control of transcription initiation. • But gene expression can be controlled after transcription, with mechanisms such as: • RNA interference • alternative splicing • RNA editing
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Posttranscriptional Regulation • RNA interference involves the use of
small RNA molecules • The enzyme Dicer chops double stranded RNA into small pieces of RNA • micro-RNAs bind to complementary
RNA to prevent translation • small interfering RNAs degrade particular mRNAs before translation 75
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Posttranscriptional Regulation • Introns are spliced out of pre-mRNAs
to produce the mature mRNA that is translated. • Alternative splicing recognizes different splice sites in different tissue types. • The mature mRNAs in each tissue possess different exons, resulting in different polypeptide products from the 76
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Posttranscriptional Regulation • RNA editing creates mature mRNA
that are not truly encoded by the genome. • For example – • apolipoprotein B exists in 2 isoforms • one isoform is produced by editing the
mRNA to create a stop codon • this RNA editing is tissue-specific
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Posttranscriptional Regulation • Mature mRNA molecules have
various half-lives depending on the gene and the location (tissue) of expression. • The amount of polypeptide produced from a particular gene can be influenced by the half-life of the mRNA molecules.
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Protein Degradation • Proteins are produced and degraded
continually in the cell. • Proteins to be degraded are tagged with ubiquitin. • Degradation of proteins marked with ubiquitin occurs at the proteasome.
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Aetiology for parkinson’s disease
• Remain largely unknown • Heredity have a limited role • Defective gene responsible for a rare
condition called autosomal recessive juvenile parkinsonism (teens and 20s) • Oxidative stress theory (environmental origin) esrmnotes.in|Class notes made easy.
Epidemiology of PD The most common movement disorder affecting 1-2 % of the general population over the age of 65 years. The second most common neurodegenerative disorder after Alzheimer´s disease (AD).
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Risk factors • •
• •
•
•
•
Age - the most important risk factor Positive family history Male gender Environmental exposure: Herbicide and pesticide exposure, metals (manganese, iron), well water, farming, rural residence, wood pulp mills; and steel alloy industries Race Life experiences (trauma, emotional stress, personality traits such as shyness and depressiveness)? An inverse correlation between cigarette smoking
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Clinical features of PD • Three cardinal symptoms:
→
→ →
resting tremor bradykinesia (generalized slowness of movements) muscle rigidity
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Clinical features of PD
Resting tremor: Most common first symptom, usually asymmetric and most evident in one hand with the arm at rest.
Bradykinesia: Difficulty with daily activities such as writing, shaving, using a knife and fork, and opening buttons; decreased blinking, masked facies, slowed chewing and swallowing.
Rigidity: Muscle tone increased in both flexor and extensor muscles providing a constant resistance to passive movements of the joints; stooped posture, anteroflexed head, and flexed knees and elbows. esrmnotes.in|Class notes made easy.
Additional clinical features of PD
Postural instability: Due to loss of postural reflexes. Dysfunction of the autonomic nervous system: Impaired gastrointestinal motility, bladder dysfunction, sialorrhea, excessive head and neck sweating, and orthostatic hypotension.
Depression: Mild to moderate depression in 50 % of patients.
Cognitive impairment: Mild cognitive decline including impaired visual-spatial perception and attention, slowness in execution of motor tasks, and impaired concentration in most patients; at least 1/3 become demented during the esrmnotes.in|Class notes made easy.
Hoehn and Yahr Staging of Parkinson's Disease •
• •
• •
Stage 1: Mild signs and symptoms on one side only, not disabling but friends notice. Stage 2: Symptoms are bilateral, minimal disability, posture and gait affected Stage 3: Significant slowing, dysfunction that is moderately severe Stage 4: Severe symptoms, walking limited, rigidity, bradykinesia, unable to live alone Stage 5: Cachectic, complete invalidism, unable to stand, walk, require nursing care esrmnotes.in|Class notes made easy.
Neuropathology of PD Eosinophilic, round intracytoplasmic inclusions called lewy bodies and Lewy neurites. First described in 1912 by a German neuropathologist Friedrich Lewy.
Inclusions particularly numerous in the substantia nigra pars compacta.
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Lewy bodies
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Neuropathology of PD: Lewy bodies
Not limited to substantia nigra only; also found in the locus coeruleus, motor nucleus of the vagus nerve, the hypothalamus, the nucleus basalis of Meynert, the cerebral cortex, the olfactory bulb and the autonomic nervous system.
Confined largely to neurons; glial cells only rarely affected.
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Lewy bodies
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Pathogenesis • Dopaminergic neuron degeneration
decreased activity in the direct pathway and increased activity in the indirect pathway • As a result thalamic input to the motor area of the cortex is reduced and • Patient exhibits rigidity and bradykinesia esrmnotes.in|Class notes made easy.
Neurotransmitter Imbalance • Basal ganglia normally contains
balance of dopamine and acetylcholine • Balance necessary to regulate posture, muscle tone and voluntary movement • Inhibition of dopaminergic activity leads to excessive cholinergic activity • In Parkinson’s, lack inhibitory dopamine and thus an increase in excitatory acetylcholine esrmnotes.in|Class notes made easy.
Functional neuroanatomy of PD Substantia nigra: The major origin of the dopaminergic innervation of the striatum. Part of extrapyramidal system which processes information coming from the cortex to the striatum, returning it back to the cortex through the thalamus. One major function of the striatum is the regulation of posture and muscle tonus.
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Parkinson’s disease (bradykinesia, akinesia, rigidity, tremor, postural disturbances) Huntington’s disease (hyperkinesia)
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Neurochemistry of PD
Late 1950s: Dopamine (DA) present in mammalian brain, and the levels highest within the striatum.
1960, Ehringer and Hornykiewicz: The levels of DA severely reduced in the striatum of PD patients. PD symptoms become manifest when about 50-60 % of the DA-containing neurons in the substantia nigra and 70-80 % of striatal DA are lost. esrmnotes.in|Class notes made easy.
Dopamine pathways in human brain
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Dopamine synthesis
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Therapy of PD: levodopa
Late 1950s: L-dihydroxyphenylalanine (L-DOPA; levodopa), a precursor of DA that crosses the blood-brain barrier, could restore brain DA levels and motor functions in animals treated with catecholamine depleting drug (reserpine).
First treatment attempts in PD patients with levodopa resulted in dramatic but short-term improvements; took years before it become an established and succesfull treatment.
Still today, levodopa cornerstone of PD treatment; virtually all the patients benefit. esrmnotes.in|Class notes made easy.
Therapy of PD: limitations of levodopa
Efficacy tends to decrease as the disease progresses.
Chronic treatment associated with adverse events (motor fluctuations, dyskinesias and neuropsychiatric problems).
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Inhibition of peripheral COMT by entacapone increases the amount of L-DOPA and dopamine in the brain and improves the alleviation of PD symptoms.
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Therapy of PD: limitations of levodopa
Does not prevent the continuous degeneration of nerve cells in the subtantia nigra, the treatment being therefore symptomatic.
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Treatment Strategies for Parkinson’s Disease • Symptomatic • Improve motor symptoms • Reduce medication side effects • Improve non-motor symptoms • Depression • Bowel/bladder problems • Mentation
• Neuroprotective • Slow disease progression • Reverse brain cell damage
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MAO-B Inhibitors • Inhibit degradation of
• MAO-I
•
• •
dopamine Increase efficacy of levodopa by about 20% Reduce “OFF” time May increase dyskinesia May have neuroprotective properties esrmnotes.in|Class notes made easy.
Other Receptor Targets of Drugs for PD
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