Cell-Cell and Cell-Matrix Junctions

Vocabulary practice flashcards covering cell-cell and cell-matrix junctions, cadherin-mediated adhesion, mechanotransduction, tight junctions, desmosomes, and gap junctions.

Anchoring Junctions

A functional class of cell junctions that mechanically tether cytoskeletal filaments to cell-cell or cell-matrix adhesion sites to transmit stresses.

Occluding Junctions

Junctions (tight junctions in vertebrates, septate junctions in invertebrates) that seal neighboring cells together to establish an impermeable barrier that segregates apical and basolateral extracellular fluids.

Channel-Forming Junctions

Junctions (gap junctions in animals, plasmodesmata in plants) that create continuous transmembrane conduits between adjacent cytoplasms, enabling direct passage of small water-soluble molecules and ions.

Signal-Relaying Junctions

Specialized cell-cell junctions (such as chemical synapses, immunological synapses, and Delta-Notch contacts) that mediate biochemical and electrical communication between cells.

Homophilic Binding

A mode of cell adhesion wherein identical transmembrane adhesion molecules on opposing cell membranes directly interact with one another.

Heterophilic Binding

A mode of cell adhesion in which a transmembrane adhesion protein on one cell binds to a distinct, complementary adhesion protein on an adjacent cell.

Claudin and Occludin

The primary four-pass transmembrane proteins that polymerize into branching sealing strands to eliminate extracellular space between adjacent plasma membranes in tight junctions.

Transcellular Glucose Transport

The polarized directional movement of glucose across epithelial cells, achieved by segregating active $\text{Na}^+$-driven glucose transporters to the apical membrane and passive glucose transporters to the basolateral membrane via tight junctions.

Adherens Junction

An anchoring cell-cell junction wherein classical cadherins bind homophilically in the extracellular space and connect intracellularly to bundles of actin filaments through catenin adaptors.

Adhesion Belt

A continuous band of cadherins and associated circumferential actin filament bundles located just basal to tight junctions in polarized epithelial sheets.

Tubulogenesis

The morphogenetic process in which an epithelial sheet invaginates and pinches off to form an epithelial tube via coordinated myosin II-driven contraction of apical adhesion belts.

Cadherins

A major superfamily of transmembrane adhesion receptors that mediate calcium-dependent cell-cell adhesion through repeating extracellular cadherin domains.

Cadherin Activation

The structural transition wherein cadherin extracellular domains transform from a flexible, floppy state to a rigid, extended conformation upon binding $\text{Ca}^{2+}$ at concentrations exceeding $1\text{ mM}$.

E-Cadherin

A classical cadherin expressed in many epithelial tissues whose genetic loss in mice causes embryonic death at the blastocyst stage due to failure of compaction.

Cell Sorting Out

The spontaneous segregation of mixed cell populations into distinct tissue aggregates determined by differences in cadherin subtype affinity and surface expression levels.

Mechanotransduction at Adherens Junctions

The recruitment of vinculin to extended, tension-unfolded $\alpha$-catenin, strengthening cytoskeletal anchorage by engaging additional actin filaments.

$\beta$-Catenin

An intracellular adaptor protein that directly binds the cytoplasmic tail of cadherin and also translocates to the nucleus to regulate gene transcription.

Lateral Inhibition

A Delta-Notch signaling contact wherein a developing neural cell displays surface Delta ligand to activate Notch receptors on neighboring cells, repressing their differentiation into neural cells.

Desmosome

A robust button-like anchoring junction that connects intermediate filaments of adjacent cells via nonclassical cadherins (desmoglein and desmocollin) embedded in a dense cytoplasmic adaptor plaque.

Hemidesmosome

A cell-matrix anchoring junction that fastens the intermediate filament cytoskeleton of an epithelial cell to the basal lamina through $\alpha_6\beta_4$ integrin and type XVII collagen.

Actin-Linked Cell-Matrix Junction

An anchoring junction that tethers intracellular actin filaments to extracellular matrix proteins via transmembrane integrins and adaptors such as talin, kindlin, and vinculin.

Connexon

A cylindrical hexameric channel complex formed by six transmembrane connexin subunits in the plasma membrane, docking end-to-end with a partner from an adjacent cell to establish an open gap junction channel.

Gap Junction Permeability Regulation

The physiological gating of connexon pore conductance by external cues, such as dopamine closing gap junctions to block the diffusion of Lucifer Yellow dye between retinal neurons.

Junctional Complex

A characteristic apical-to-basal arrangement of cell junctions in epithelial cells consisting of an occluding tight junction, an adherens junction, and desmosomes.