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39 Cards in this Set

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lipid raft
thicker region of the plasma membrane that contains a lot of glycosphingolipids and contain receptors for toxins
integral protein diseases
blood clotting issues, cancer - integrin

myasthenia gravis - AChR - excitation responses affected

cystic fibrosis - CFTCR - Cl- channel - misfolded protein can't make it to cell surface
peripheral protein diseases
muscular dystrophy - dystrophin

cardiac arrhythmias - ankyrin - ion channels in cardiac membrane

sickle cell disease - spectrin

proteinuric kidney disease - dynamin - cell permeability
GPI linked protein disease
cancer - Ras
How does integrin link actin to the ECM?
2 methods

One end of integrin is bound to the ECM and passes through the plasma membrane. It binds to Talin, which forms a complex with Vinculin and together they bind Actin.

Integrin again binds to ECM and passes through PM but binds to alpha actinin which then binds actin.
How does blood clotting work and how does Integrilin prevent the process from taking place?
Fibrinogen normally binds to integrilin molecules on 2 different platelets, forming a clot. Integriling (RGD tripeptides) bind to Integrin, thus blocking Fibrinogen and preventing the blood from clumping.
Describe the Spectrin membrane skeleton in RBCs
Spectrin molecules (long thin proteins) bind to Ankyrin (globular proteins) and actin. Ankyrin interacts with Band 3, and integral membrane protein, to connect this meshwork to the PM. Actin also binds to Band 4.1 which binds to glycophorin, an integral membrane protein.
basic mechanism of muscular dystrophy
Cells that lack dystrophin leak MG53, a key component of cell membrane repair, when they are damaged, leading to degeneration of muscle
N cadherin
provides signal for neurite formation
Zonula Occludens (Tight Junction)
prevent intercellular transport

transmembrane proteins = claudin and occuldin (claudin is a water channel woven within occludins)

ZO-1 and ZO-2 are cytoplasmic proteins that bind to Actin
Zonula Adherens / Adheren Junctions
transmembrane protein = cadherin

cytoplasmic proteins = catenin --> vinculin --> alpha actinin which bind actin filaments
Macula Adherens / Desmosome
found in areas with a lot of stress like cardiac muscle and skin

transmembrane proteins = desmoglein and desmocollin

attachment plaque is made of desmoplakin and plakoglobin which binds intermediate filaments
Gap Junction
Consists of connexons, which are made of 6 cylindrical subunits called connexins

cytoplasmic proteins = ZO-1 and Drebrin that bind actin

Mutations:
Connexin 26 - inherited deafness
Connexin 50 - cataracts in lens
Hemidesmosome
adhere epithelial cells to basal lamina

transmembrane proteins = integrin and BP 180

cytoplasmic proteins = BP230 and plectin which bind intermediate filaments
Kartagener's syndrome
a tyope of Primary Cilia Dyskinesia

absence of dynein arms on microtubules leads to immotile cilia in the respiratory tract
primary cilia
sensors of fluid flow

passive bending as a result of fluid flow in a kidney tubule opens polycystin 1&2, mechanoreceptor calcium channels
major functions of cell membranes
structure, protection, activation of cell, transport, cell to cell interaction
functions of integral membrane proteins
channel (pore), transporter (carrier), receptor, enzyme, cytoskeleton anchor, cell identity marker
subdomains of ER
smooth, rough, nuclear, export sites
unfolded protein response
series of signaling cascades that respond to environmental stress and developmental cues - slow down translation and increase molecular chaperones that assist in correct folding of proteins
chronically activated UPR
occurs in conditions of low O2, high or low blood glucose - leads to inflammation in obesity and atherosclerosis, diabetes, cancer
enlarged, dilated cisternae of ER
hydropic swelling of liver cells due to toxic injury
progeria
normally lamin A is farnesylated and then the lipid is cleaved off but in progeria the cleavage site is deleted so lamin becomes progerin --> abnormal nuclear morphology, progerin in mitotic cytoplasm, binucleation
post translational targeting / import
proteins are assembled on free ribosomes and are distributed to cytoplasm, nucleus, peroxisome, mitochondria
co-translational targeting / import
proteins are made on RER ribosomes and are distributed to the ER, Golgi, plasma membrane and lysosome
How are proteins targeted to the ER?
Signal Recognition Particle (SRP) binds to signal sequence of mRNA, arresting translation. SRP interacts with a docking protein on the ER membrane and is then released, allowing translation to continue. Signal sequence interacts with translocator channel protein so ribosome - ER interaction is stabilized. Signal peptide is cleaved off by signal petidase and is digested. Protein is released into lumen of ER.
actin mRNA zip codes
3' untranslated sequence - needed to localize actin mRNA to specific regions of the cell - can block this polarization using oligonucleotides
Cystic Fibrosis Transmembrane Conductance Regulator
Cl- channel in epithelial cells

in CF, it gets misfolded so it can't reach the membrane

can add chaperones in the hopes of getting it to properly fold - BiP (binding protein)
Smooth ER functions
conversion of glycogen to glucose in the liver, storage of calcium in the sarcoplasmic reticulum, detoxification via oxidative enzymes like P450s, synthesis of steroid hormones in gonads and the adrenal cortex
COPII
associates with the membrane at ER export sites to facilitate budding

coat is assembled via Sar1, Sec 23 - Sec 24, Sec 13 - Sec 31

concentrates cargo and bends ER membrane to create transport vesicle for delivery to Golgi (anterograde)
parts of the Golgi
ERGIC (ER - Golgi Intermediate Compartment)
cis face
medial face
trans face
trans Golgi Network
I Cell Disease
defect in adding Mannose 6 phosphate to lysosomal enzymes ==> there's a build up of substances in lysosomes and the proteins are excreted instead of imported into lysosome
Vesicular tubular cluster
aka ERGIC

mediates trafficking between ER and Golgi - facilitates sorting of cargo
COPI
coats vesicles that move Golgi to ER (retrograde)
V SNARES and T SNARES
transmembrane proteins on vesicles and target sites that bind together, leading to immediate fusing of membranes

can be destroyed by toxic enzymes, affecting exocytic processes which can lead to failure of muscle to contraction
types of endocytosis
phagocytosis, macropinocytosis, clathrin mediated, caveolin mediated, plain ole pinocytosis
Familial Hypercholesterolemia
High serum levels of LDL due to a mutation in binding to receptors (normally found in coated pit regions of the plasma membrane)
clathrin mediated endocytosis
AP2 binds to transmembrane receptor and clathrin to form a lattice structure. Dynamin helps pinch off the pit. Inside the cell, clathrin and adaptins disassemble via HSC70 and auxillin (accessory molecules) and are recycled.
caveloae
invaginations in membrane - lipid subdomains rich in sphingolipids and cholesterol

coated with caveolin protein

preferred means of entrance by pathogens because it doesn't feed into lysosomal pathways