Trafficking to the Apical and Basolateral Membranes in Polarized Epithelial Cells

Abstract

Renal epithelial cells must maintain distinct protein compositions in their apical and basolateral membranes in order to perform their transport functions. The creation of these polarized protein distributions depends on sorting signals that designate the trafficking route and site of ultimate functional residence for each protein. Segregation of newly synthesized apical and basolateral proteins into distinct carrier vesicles can occur at the trans-Golgi network, recycling endosomes, or a growing assortment of stations along the cellular trafficking pathway. The nature of the specific sorting signal and the mechanism through which it is interpreted can influence the route a protein takes through the cell. Cell type-specific variations in the targeting motifs of a protein, as are evident for Na,K-ATPase, demonstrate a remarkable capacity to adapt sorting pathways to different developmental states or physiologic requirements. This review summarizes our current understanding of apical and basolateral trafficking routes in polarized epithelial cells.

Cystic Gene Dosage Influences Kidney Lesions After Nephron Reduction

“…It has been suggested that, in inherited PKD, the translocation of transporters from the basal to the apical membrane may participate to cysts enlargement through an increase of fluid secretion [7,26]. In the present study, we failed to detect any change of the apico-basal polarity in cells lining tubular dilations.…”

“…PKHD1 encodes for fibrocystin, a large transmembrane protein whose function is still unknown [5]. Despite differences in the age of onset, the severity of the disease or the localization of the cysts, it has been suggested that common mechanisms are involved in cyst formation, including cell proliferation and apoptosis [6], disturbance of cell polarity and cell-matrix interaction [7], enhanced fluid secretion, or loss of oriented cell division [8]. On the other hand, the primary cilium as well as calcium signaling have been suggested to play a role [9,10,11,12].…”

Loss of kAE1 expression in collecting ducts of end-stage kidneys from a family with SLC4A1 G609R-associated distal renal tubular acidosis

“…Such cell-line-specific differences in protein trafficking proteomes may explain classical differences in polarized expression among independent clones of the same cell type [41]. Similar differences in SLC4A1 dRTA mutant polypeptide targeting were recently observed in polarized cell lines and in mice.…”

The secretory pathway at 50: a golden anniversary for some momentous grains of silver

“…At least in epithelial cells, sorting along the secretory pathway is not limited to the dichotomous allocation of proteins into shared carriers bound for the apical or the basolateral surface. It appears that in many and perhaps in most cases, proteins bound for delivery to the same subdomain of the plasma membrane are transported by distinct cadres of carrier vesicles that pursue different itineraries and that manifest specific biochemical properties (Farr et al , 2009, 2015; Stoops and Caplan, 2014; Stoops et al , 2015). The growing number and variety of these pathways suggests the intriguing possibility that each newly synthesized protein may follow its own customized variation on the secretory pathway and be packaged into vesicles that carry no other cargoes.…”