basolaterally

Basolaterally is an adverb used to describe something occurring on, or directed toward, the basolateral domain of a polarized cell, especially epithelial cells. The basolateral domain comprises the portions of the plasma membrane that face the underlying tissue (basal side) and the membranes that contact neighboring cells (lateral sides). This term contrasts with apically directed phenomena, which occur at the apical surface facing the lumen or external environment. The word derives from basolateral, itself formed from baso- (base or basal) and lateral.

In polarized epithelia, basolateral localization supports directional transport between the bloodstream and underlying tissues or across the epithelium. For example, many transport proteins such as Na+/K+-ATPase are situated basolaterally to maintain ion gradients and drive secondary active transport. The apical surface often hosts nutrient uptake or secretion into the lumen, while the basolateral surface interfaces with underlying tissue and bloodstream. Tight junctions help maintain the separation between apical and basolateral compartments.

Basolateral targeting is guided by cellular sorting mechanisms that direct proteins to the correct membrane domain. Sorting signals in protein cytoplasmic tails, adaptor protein complexes (such as AP-1B), and endocytic pathways contribute to basolateral trafficking. Mislocalization of proteins to the basolateral surface can disrupt epithelial polarity and function, with potential implications for disease.

In usage, basolaterally is employed to describe the location or direction of a process, such as basolaterally localized receptors or basolaterally directed trafficking, within studies of cell polarity and transport.