exclude molecules from apical and basal side so that they can selectively pass 1. barrier funciton 2. fence function 3. signaling function

Cell Junctions Flashcards by Sara Fieger

four classes of cell junctions

anchoring
occluding
channel forming
signal relaying

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anchoring junctions

control cell to cell adhesions and cell matrix adhesion

connected to cytoskeletal inside the cell

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actin filament attachment cites in anchoring junctions

either adherens or actin linked cell matrix adhesions

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intermediate filament attachment sites in anchoring junctions

desmosomes

hemidesmosomes

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occluding junctions

seals gaps between cells so that epithelium is impermeable barrier

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channel forming junction

creates passage way for small molecules and ions to pass from cell to cell

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signal relay junction

allows signals to be related from cell to cell across their plasma membrane at cell to cell contact

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list of type of junctions on slide 99

top to bottom

tight junction

adherents junction

desmosomes

gap junction

then on floor is actin linked cell matrix adhesion and hemidesmosome

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list junction types from apical to basal

occluding

cell to cell anchoring

channel forming

cell matrix anchoring

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what is an example of homophillic adhesion?

catenins

highly selective recognition in tight junctions

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cadherins are __ dependent and bind to ___

calcium dependent, bind to like (homophillic adhesion)

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what links classical cadherins to cytoskeleton

B-catenin, p120 catenin, y-catenin

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2 superfamilies of cadherin

classical

nonclassical

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classical cadherins

main mediators of Ca2+ dependent junctions

E cadherin (most) (epithelial cells, brain) 
N cadherin (muscle, nerve, lens)
VE cadherin (endothelial cell
P cadherin (placenta)

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nonclassical cadherins

include desmocollins and desmogleins that form desmosome junctions

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True or false?

none of the adhesion molecules are bound directly to cytoskeleton

true

they all must have linker proteins on cytoplasmic side (i.e. catenins)

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tight junctions

exclude molecules from apical and basal side so that they can selectively pass

barrier funciton
fence function
signaling function

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what anchors tight junctions to actin cytoskeleton

what anchors adherent to eptiheleium

adhesion belt

molecules involved in polarity

downstream of cadherins coming together

Par
Crumbs
Scribble

what type of junctions has size restrictions?

gap junction

allows ions and very small molecules (i.e. glucose)

1000 Daltons (1 kD)

what are the proteins that make up gap junctions?

connexins

make up gap jxns

continually removed and replaced

can be same (homo) or different (hetero)

basal lamina is made of

laminin

collagen type IV

bidirectional signaling

information can flow from extracellular in or intracellular out this is a characteristic of basal lamina

focal adhesions

link ECM to thru integrin receptor to actin cytoskeleton if unstable -- nascent

focal contacts

sites in the ECM, integrins, and cytoskeleton interact

FAK

cytoplasmic tyK recruited by talin or pazillin and provide docking site for Src kinase

extraceulluar macromolecules of matrix

GAGs | fibrous proteins

GAGs

covalently linked to proteins to form proteoglycans -- ground substance

fibrous proteins

collagen and fibronectin structural and adhesive

Laminin

primary organizer of sheet structure classical laminin (a, b, y)

type Iv

tensile strength to basal lamina superhelix of 3 proteins

what links laminin and Type IV collagen?

nidogen and perlecan

integrins

span membrane with short C terminal tail and long N terminal bind to form cytoskeleton

integrins

utilize laminin and type IV dimeric they're the anchor to the basal lamina

activation of integrins requires what protein?

focal adhesion kinase

inside out activation

intracellular signals cause talon to move to a-b linkage, integrin is active

signal to integrin can come via

outside (substrate) inside (signal)

what type of cells make up ECM?

fibroblasts

GAGs

big squishy part of ECM lubricate and connect things HUGE proteoglycans sugars connected to proteins connected to another protein

hyaluronic acid

long stem on the GAGs building block highly hydrated, takes up lots of space squishy

collagen

all the cross linking takes place in ER fibroblasts ER is where collagen assembly takes place

what is essential for the affinity of collagen fibers?

Poly/Lysl hydroxylases for all the pro filaments really defects of these enzymes or lack of the substrates