Cell Junctions and Extracellular Matrix

Flashcards for lecture notes on cell junctions and extracellular matrix.

Extracellular Matrix (ECM)

A complex network of macromolecules (proteins, polysaccharides) made and secreted by cells that fills the spaces between cells and lies beneath epithelial/endothelial cells.

Interstitial Matrix

Fills the spaces between cells; type of ECM organization.

Basement Membrane

A thin layer of specialized ECM that lies beneath all epithelial/endothelial cells; type of ECM organization.

Collagen

Fibrous proteins (e.g., collagens, elastin); major class of macromolecules in ECM.

Glycosaminoglycans (GAGs)

Large and charged polysaccharides, usually covalently linked to a protein forming proteoglycans; major class of macromolecules in ECM.

Fibronectins

Multi-adhesive glycoproteins (e.g., fibronectins, laminins); major class of macromolecules in ECM.

Collagen Fibers

Larger, cable-like bundles of collagen visible in the light microscope.

Collagen Fibrils

Thin structures (10–300 nm in diameter) visible in electron micrographs that often aggregate into collagen fibers.

Osteogenesis Imperfecta

Disease connected to Collagen I.

Elastin

Protein of elastic fibers, rich in proline and glycine, but not glycosylated.

Tropoelastin

Soluble precursor of elastin.

Marfan Syndrome

Disease connected to Fibrillin 1.

Disaccharide units

Repeating sugar + amino sugar units that compose GAGs.

Hyaluronan (hyaluronic acid)

GAG that forms large aggregates with aggrecan and collagen II in cartilage.

Multi-adhesive glycoproteins

Help organize the matrix; have multiple domains with specific binding sites for other matrix macromolecules and cell surface receptors.

Cellular Fibronectin

Multiadhesive protein of the interstitial matrix, produced by fibroblasts.

Plasma Fibronectin

Multiadhesive protein produced by hepatocytes and secreted into the bloodstream.

Laminins

Multiadhesive proteins of the basal laminae, composed of three polypeptides (α, β, and γ).

Basement Membrane (BM)

ECM in direct contact with the basal domain of epithelial, endothelial, and mesothelial cells, visible under the light microscope after staining with PAS.

MMPs

Matrix MetalloProteinases, most important group of degrading enzymes, zinc containing proteins.

CAMs

Cell adhesion molecules responsible for cell-cell adhesion.

Occluding junctions

Form a tight seal between adjacent cells; allow a cell sheet to function as a barrier.

Anchoring Junctions

Anchor cells together or to ECM; provide mechanical stability.

Communicating Junctions

Allow direct communication between adjacent cells.

Macula

Cell junction in the form of a spot or punctate area of limited extent.

Zonula

Cell junctions like a belt or girdle around the cell.

Tight junction (TJ)

Beltlike band of sealing strands that encircle each cell in the sheet; also known as Zonula Occludens (ZO).

Claudins

Transmembrane proteins that confer barrier properties of tight junctions and form charge (ion)-selective small pores.

Adherens junction

Belt-like configuration around the cell that holds epithelial cells and endothelial cells together; also known as Zonula adherens (ZA).

Desmosome

Spot-like cell-cell adhesions that provide mechanical strength.

Gap junction (Nexus)

Bridges gaps between adjacent cells, creating direct channels from the cytoplasm of one cell to that of the other.

Pemphigus

Autoimmune skin disease involving antibodies against desmosomal cadherin proteins.

Naxos disease

Arrhythmogenic right ventricular cardiomyopathy (ARVC) caused by Plakoglobin gene mutation.

Hemidesmosomes

Asymmetrical structures anchoring the basal domain of an epithelial cell to the underlying basal lamina.

Bullous pemphigoid (BP)

Blistering disease of the skin caused by defects in hemidesmosome components.

Focal Adhesions

Dynamic structures creating a link between the actin cytoskeleton and extracellular matrix proteins via integrins.