Localization, Trafficking, and Significance for Acid Secretion of Parietal Cell Kir4.1 and KCNQ1 K+ Channels

TRIM50 Protein Regulates Vesicular Trafficking for Acid Secretion in Gastric Parietal Cells

“…2B). In contrast to H ϩ /K ϩ -ATPase, KCNQ1 channels localized in tubulovesicles do not undergo the histamine-induced subcellular translocation during acid secretion (26). Taken together, our histochemical observations likely suggest that TRIM50 resides in the cell interior canaliculi generated by tubulovesicular fusion during the stimulated phase.…”

KCNE2 and the K+channel

“…4,30,31 The latter two would seem ideal: inward rectifier K + channel a subunits only contain two TM segments, lacking the intrinsic voltage sensor domain that would necessitate cellular depolarization for their activation, and hence possess the capability to be constitutively active at negative voltages (parietal cells are thought to spend most of the time between -20 and -40 mV). Their current is only attenuated at more depolarized voltages owing to intracellular block of their elongated pore by Mg 2+ and polyamines such as spermine and spermidine.…”

Functional Transformation of Gastric Parietal Cells and Intracellular Trafficking of Ion Channels/Transporters in the Apical Canalicular Membrane Associated with Acid Secretion

“…In contrast to the stimulation-associated translocation of H ϩ /K ϩ -ATPase, only a portion of the total pool of KCNQ1 translocates to the apical canalicular membrane after stimulation, the rest remaining in the cytoplasm, suggesting an association with H ϩ /K ϩ -ATPase-free microsomal vesicle fractions 28,29,34,35) (Fig. 4).…”

“…34,36) Immunogold electron microscopy demonstrated that Kir4.1 was detected on neither intracellular tubulovesicles nor basolateral membrane, but exclusively on the apical canalicular membrane of parietal cells. 36) Although its specific localization at the apical canalicular membrane suggests that Kir4.1 may participate in the K ϩ -recycling pathway, its intracellular trafficking to this membrane remains to be elucidated, including the regulatory mechanism of the molecular transport.…”