basolateral

Basolateral describes the region of a polarized epithelial cell that faces the interior of the tissue: the basal surface adjacent to the basement membrane and the lateral surfaces that contact neighboring cells. It is contrasted with the apical domain, which faces the lumen or outside world. Epithelia exhibit cell polarity that localizes specific proteins to distinct surfaces; the basolateral membrane typically houses transporters and channels responsible for uptake from or release into the extracellular fluid, while the apical membrane mediates absorption from the lumen.

Tight junctions and adherens junctions separate apical from basolateral domains, maintaining polarity. The basal surface also adheres to the basement membrane, a specialized extracellular matrix that anchors the tissue; integrins mediate this adhesion and participate in signaling.

Functional examples: in intestinal and renal epithelia, the Na+/K+ ATPase pump is usually localized basolaterally, maintaining Na+ and K+ gradients; nutrients absorbed from the lumen on the apical side are transported across the cell and released basolaterally.

Basolateral polarity is essential for directional transport, barrier function, and tissue organization. Disruption of polarity or mislocalization of basolateral proteins can occur in disease and cancer.

Terminology: the term basolateral is sometimes used to describe the entire basal plus lateral surface of a cell, as opposed to the apical surface facing the lumen.