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Cell Biology - Class 04
The in-depth study of human cells
By: David Botton

Cell Adhesion


Cell Adhesion

junctions

ocluding / tight junctions

created through integral protiens:

occludin + occludin

claudin + claudin

create barrier to prevent entrance of anything between cells = paracellular diffusion barrier

"cap"

cadherin related

(zonula) adherens (aka belt desmosomes)

"seem"

(spot) desmosomes (aka Macula adherens)

"reinforcement"

gap junction

6 connexins create a connexon

2 connexon of adjacent cells adhere to form gap

purpose: action potential and Ca pass through

can be open or closed

hemidesmosomes

Basement membrane

connects epithelial tissue to connective tissue

2 sections

basal lamina

made of

laminim

type 4 collagen

protoglycans

reticular lamina

made of

collagen

integrin hooks epithileal tissue to basement membrane laminim in basal lamina

additional connective tissue basil to reticular to main connective tissue

Definition

attachment of cells to each other to create tissues

Principals

cell adhesion molecules (CAM) in membrane

cadherins

ligand: cadherins

Ca++ dependent

connects epithelial and muscle cells

at cell jucntions

(zonula) adherens (aka belt desmosomes)

cadherins are arranged in strips on sides

catenins link (are combining component) of cadherins to actin of cytoskeletin 

enables vibrations in one cell to be felt in other

plaque (a peripheral protein) cements cadherins to cell wall from with in

(spot) desmosomes (aka Macula adherens)

plaque anchors each cadherins to cell wall from with in

plaque has keratin filaments to further anchor in cell directly

spot reinforcement of zonula adherens

E-cadherin to E-cadherin

E- (for epithileal), N- (for nerves), P- (platelets and epithilelal)

always two together = dimer

connected by calcium bond to each other at binding site

on dimer connects to other dimer via calcium bond at binding sites

homophilic interaction (cadherin + cadherin)

purpose: create permanent sheets of epithelium

selectins

ligand: polysaccharide

designed to glycoproteins of another cell

Ca++ dependent

CRD - Carbohydate Recognition Domain = Binding site of selectins turned on by calcium

types

L-Selectin (Leukocytes)

to E-Selecting

E-Selecting (Epithelium)

to L-Selectin

 P-Selectin (Platelets)

to Mucins (PSGL-1)

purpose: to connect temporary WBC with Epithelial cells of blood vessel wall

also with integrin to Ig-CAM at same time

integrins

ligand: fibromnectin, laminin, fibrinogen, ig-cam

not dependant on Ca++

actions

binds cell to matrix in connective tissue

connects to cytoskeletin

know integrins on pg 515

LFA-1

connected to ig-CAMs (between white blood cells and endothelial cells)

MAC-1

connected to ig-CAMs (between white blood cells and endothelial cells)

Laminin

cell matrix connection

Fibronectin

cell matrix connection

(GPIIb/GPIIIa) Fibrinogen

platelet aggregations

has alpha and beta sub unit

linked by various proteins to actin of cytoskeletin

immunoglobulins

ligand: other CAM

not dependant on Ca++

know

ICAM-1

intercellular

ICAM-2

VCAM-1

vascular

NCAM-1

neuro

CD4

in T4 cells - helpers

CD8

T-attack / suppressor cells

prupose: white blood cell interaction with endothelium (simple squamus style) cells

all our integral membrane proteins

CAM associated to a ligand

cell controls adhesion

through surface density of CAMs

state of agregation

to move next to other cell

state of activiation

to turn on CAMs

Rate of ligand binding and association

CAMs interact with cytoskeletin of cell

for movement

CAM + Ligan can activate cellular intracellular signal transduction pathways

(c) 2005 All Rights Reserved - David Botton