MMT: structure and function of the ECM

Question 1

Name the 2 primary types of extracellular matrix

Answer 1

connective tissue and basal lamina

Question 2

Describe functional and structural differences between the 2 primary types of extracellular matrix

Answer 2

connective tissue: space filling ECM. largely composed of various cells, fibrillar proteins, proteoglycans, and glycosaminoglycans

basal lamina: thin layer of assembled proteins that epithelial cells sit on top of. includes lamina, collagen 4, heparan sulfate proteoglycan, and nidogen

Question 3

identify key structural entities in the procollagen molecule and specify the functional significance of these elements

Answer 3

It has a triple helical domain, and a cleaved N-propeptide and C-propeptide, and non-helical telopeptides. The helical domains cross link via non helical telopeptides being modified

Question 4

What is the primary cell type that secretes fibrillar collagens and other ECM components

Answer 4

fibroblasts

Question 5

Describe the role of proteoglycans in influencing collagen fibril assembly

Answer 5

Small leucine rich proteoglycans (SLRPS) facilitate the organization of fibrils head to tail, preventing their lateral interaction. One the length is correct, the fibrils can then grow in thickness

Question 6

Describe the critical functional roles of proteoglycans and glycosaminoglycans in the connective tissue

Answer 6

proteoglycans: they provide support and cushioning, they fill space to help the tissue maintain its integrity, and they can help regulate cell behavior

GAGs: hydrate and lubricate tissue, shock absorption, and cell communication

Question 7

Describe the role fibronectin plays in ECM assembly and understand how force generation via the actin cytoskeleton facilitates fibronectin assembly.

Answer 7

Fibronectin in the extracellular space is connected on the cytoplasmic side to actin cytoskeleton via integrins. As the integrins move through the membrane, they unfold dimers of fibronectin fibrils. This forms unfolded linear fibronectin fibers, that create a network. this network further supports assembly the of ECM

Question 8

briefly describe fibronectin

Answer 8

It is the master ECM protein; it can bind with other ECM proteins and organize the complex structure and help it bind with cells

Question 9

Specify the primary extracellular matrix proteins that compose basement membranes.

Answer 9

Collagen: not fiber forming, instead it is network forming

Laminin: assembles into a network and is primary in contact with basal surface of the cells

Nidogen and heparan sulfate proteoglycan: connect and stabilize collagen and laminin

Question 10

Identify the proteins that self-assemble to form a sheet-like structure in the basement membrane

Answer 10

Collagen IV; they can assemble into dimers at the N terminal and tetramers at the C terminal; this gives them their network characteristic as opposed to being linear