ECM and cell junctions

what does the ECM function to do?

provide support, strength/organization, a barrier, signaling for growth/survival/differentiation.

what are the three major molecules of the ECM?

• adhesion proteins

• structural proteins

• proteoglycans

what is collagen?

a structural protein most abundant in the ECM that is made from one of five types of fibroblasts.

describe the secretion of collagen

processed by proteases that form ECM around itself.

crucial in wound healing.

describe collagen of the cornea vs tendons

collagen in the cornea are orthogonally organized to create transparency

collagen in the tendon are organized parallel to create strength and flexibility.

list side effects of collagen disorders

abnormally stetchy skin, fragile, hypermobile. lack of enzyme that converts procollagen to collagen

what is elastin

a protien that provides elasticity, strength, recoil. in your skin lungs and blood vessels. works with collagen and declines with age.

what are proteoglycans?

proteins that provide cushioning, space filling, hydration, regulation of signaling molecules.

wht are two examples of proteoglycans?

aggrecan (cartilage), decorin ( collagen)

what is fibronectin?

modular proteins with domains for collagen, heparing, fibrin and cell binding.

• bridges ECM with integrins

• guides cell migration and adhesion

what is laminin?

bridges ECM by binding collagen, proteoglycans, integrins that stengthens the basement membranes and provides structural scoffolding.

what is the basal lamina?

specialized ECM at the interface between cells and the connective tissue composed of collagen 4, laminin, and proteoglycans.  

• provides barrier, and regulation cell b ehaviour and signaling

what is ECM remodeling?

MMP’s degrade the ECM to rebujild it however it needs

• roles in wound healing

  • regulated by tissue inhibitors of MMPs

describe the different epithelial sheets

singlular layer of epithelium is considered simple.

multipl.e layers considered straitified.

what are integrins?

transmembrane proteins that link ECM to cytoskeleton via adaptor proteins that enable adhesion to ECM and other cells

what are t6he structures of integrins?

alpha and beta heterodimers that switch between bent (inactive) and extended (active). any protein that can bind has RGD.

explain signaling and disease in relation to integrins

outside in ECM binds to FAK/src that activates molecule for survival, motility and invasion.

has clinical relevance in cancer invasion.

what are actin linked cell junctions and what do they do?

link ECM to actin filaments to basla lamina to function as dynamic adhesions and force transmission.

what are hemidesmosomes?

andhoring proteins that anchor IF to basal lamina through integrins.

• provieds strong cell adhesion to ECM to resist mechanical stress.

  • epidermylosis bullosa is a fragile skin disorder that causes blistering from the skin layers seperating from the basal lamina.

what are desmosomes?

on lateral membranes below adherens to connect IF across cells. cadherins are specialized desmogleins.

what do cell junctions funciton to do?

• cell communication

• tissue strength

• transpolrt between cells

  • selective barrier

what are tight junctions?

barrier

seal adjacent cells at the apical surface that regulate paracellular transport.

establishes apical-basal polarity

what are adheren junctions?

below tight junctions to link actin filaments across neighboring cells and provide mechanical strength.

cahderins a key molecule here`

what ate gap junctions?

direct channels beyween neighboring cells

explain the big picture of ECM proteins, integrins, and cadherins.

• ECM proteins ( collagen, laminin, fibronectin) provide structural scaffold

• cadherins connect cell to cell

• integrins link ECM to cytoskeleton