Molec and Cell Chapter 19

Tight junctions

Seals gap between epithelial cells. and a Fence Between Plasma Membrane Domains

selective permeability barriers

Adherens Junction

Connects Actin filament bundle in one cell with that in the next cell.

Respond to Forces Generated by the Actin Cytoskeleton

Desmosome

Connects intermediate filaments in one cell to those in the next cell.

Give Epithelia Mechanical Strength

Disease:Pemphigus

Gap Junction

Allows the passage of small water-soluable molecules from cell to cell

Couple Cells Both Electrically and Metabolically-connective tissues, epithelia, heart muscle cells

Hemidesmosome

Anchors intermediate filaments in a cell to extracellular matrix

Cadherins

Are Cell to Cell, Ca2+ dependent

Mediate Homophilic Adhesion • N terminal tips are site for Homophilic binding

Integrins

Are Cell to Matrix; Link the Extracellular Matrix to the Cytoskeleton

Cadherin-Dependent Cell–Cell Adhesion

Guides the Organization of Developing Tissues, and is Selective cell-cell recognition • Specific binding of cadherins

Fibroblast-L cells

Rho

promotes formation of actin myosin stress fibres at Cell cortex

Rac

inhibits formation of fibres and promotes branched actin network.

Catenins

Link Classical Cadherins to the Actin Cytoskeleton at adheren junctions

Claudins

prevent loss of water

Occludins

limits junctional permeability

Tricellulin

Seals cell membranes together,prevents leakage, in tricellular junction

Scaffold Proteins

Organize Junctional Protein Complexes

A Gap-Junction Connexon

Is Made of Six Transmembrane Connexin Subunits

Selectins

mediate transient cell-cell adhesions in blood stream; Require Ca for adhesive function; They help WBCs attach to blood vessel walls, which allows the cells to exit the bloodstream and enter tissues where they’re needed.

L-selectin

found on white blood cells

P-selectin

found on platelets and on endothelial cells activated by inflammation

E-selectin

found on activated endothelial cells

ICAMS

intercellular cell adhesion molecules (Heterophilic binding to integrins)

VCAMS

vascular cell adhesion molecules (Heterophilic binding to integrins)

NCAMs

neural cell adhesion molecules; Homophilic binding to integrins ▪ Can inhibit adhesion

fibroblasts

The ECM is made locally by cells, mainly ________?

GAGs (Glycosaminoglycans)

Occupy Large Amounts of Space and Form Hydrated Gels; Usually attached to proteins → proteoglycans. Form a gel that resists compression and allows fast diffusion of nutrients.

Hyaluronan

space filler during tissue morphogenesis and repair; Resists compressive force in tissues and joints

Proteoglycans

Are Composed of GAG Chains Covalently Linked to a Core Protein-large with COLLAGEN

Made in ribosome Outside of cell

DECORIN

binds to collagen fibrils and regulates fibril assembly and fibril diameter

SYNDECAN

Integral component of plasma membrane, not secreted, influences cell growth and proliferation, intracellular domain interacts with actin. Found in fibroblasts and epithelial cells

COLLAGEN

resist tension; They have non helical domains=Flexibility

Elastin

Gives Tissues Their Elasticity. Mutation in fibrillin leads to Marfan’s syndrome:

Fibronectin

Binds to Integrins and is made of repeats of FN1,2 and 3; Two type III repeats near the C-terminus, Help Organize the Matrix

Basal Lamina

known as Basement membrane, Made up of Laminin , Type IV Collagen.

Type IV collagen mutation

ALPORT SYNDROME (irregularly thickened, dysfunctional glomerular filter

Inactive Integrins

Folded and hooked in cytosolic tail, cannot bind to matrix protein

Active Integrins

Unhooked, exposes external and internal binding sites