Animal Cell Extracellular Matrix and Cell Adhesion: Key Proteins and Signaling

What are the insoluble secreted molecules around animal cells

Extracellular matrix

What is the extracellualr matrix?

Molecules made of both proteins and sugars that surround/fill in the spaces between animal cells (BINDS CELLS AND TISSUES TOGETHER)

What is basal lamina?

a sheetlike form of extracellular matrix found in connective tissue, provides structural support (for epithetial tissue)

Structural proteins in matrix

they are tough and fibrous in gel like sugars (adhesions proteins link it together, specifically ECM with cells)

MAJOR ONE: Collagen

Collagen

MOST ABUNDANT PROTEIN IN ANIMAL TISSUE

40 protein structures is considered it

3 polypeptides in helix shape (Gly (smallest protein)-X-X)

Collagen fibers or fibrils

Type 1 collagen make up 90% of collagen

Staggered assembly done outside of cell

Covalent cross links are between helices

Elastic fibers

Made of elastin

Found in connective tissue

Can stretch/snap back when tension is applied /released

Polysaccharides in ECM

Glyoaminoglycans or GAGs are very negatively charged and attach to serines

GAGs + proteins= proteoglycans

100s/core protein

Adhesion Proteins

BINDING SITES FOR INTEGRINS

Links ECM parts with itself and cell surface

Interacts with collagen and protoglycans

MAJOR ADHESION PROTEIN

Fibronectin

Laminin

part of basal lamina

mesh like network that also provides binding sites for intergrins

Intergrins

cell surface receptor proteins

attaches ECM to cells

"anchor"

makes cell-matrix junction stable

has alpha-beta subunits

Focal adhesion

links actin to ECM (for migration and signaling)

Hemidemosomes

Anchors intermediate filament to basal lamina for strong adhesion in epithetial cells with intergrins

Adhesion junction

one cell adheres to another

Occurs below tight junctions/ with desmosomes cadherins

Tight junctions

Serves as barriers to epithetial cells

Gap Junctions

Direct connections between cytoplasms of adjacent cells

Cell signaling and communication is through...

signaling molecules (cell binding to receptors of another cell or themselves)

Juxacrine signaling

Direct cell to cell signlaing via secreted molecules

"Neighbors touching"

Endocrine signaling

long range signaling

Ex: hormones

Paracrine signaling

short range signaling (to nearby target cells)

Autocrine signaling

cell responding to self made signaling molecule

ANYTHING HORMONE BASED IS

INTRACELLULAR

What can cross boundaries?

Small signaling molecules

Communication inside cells often involves...

second messengers (small diffusible molecules) known as intermediates

ex: IP3 (binds to receptrors-> release of Ca to cytosol)

G protein coupled receptors

membrane receptors that detect molecules i.e hormones to activate G proteins

Second messangers of G proteins

lipids and Ca+

Strong activation of Rho GTpase

Cancer progression and metastasis

What is "cell death"

Apoptosis

What is the cellular signal for death?

FAS (is an extrinsic outside signal; part of TNF super family)

Once CASPASES 3 IS ACTIVATED...

cell is dead

What affects cell function?

Cell adhesion and cytoskeleton organization

What initates signaling pathways?

receptors responsible for cell adhesion

Growth factors->cytoskeletal alterations-->cell movement/change in shape

What can act as receptors in cells?

Parts of cytoskeleton (targets signaling pathways)

Do signaling pathways act independently?

No, theree are signaling networks