Bc. Calhoun et al., RAB11A REDISTRIBUTES TO APICAL SECRETORY CANALICULUS DURING STIMULATION OF GASTRIC PARIETAL-CELLS, American journal of physiology. Cell physiology, 44(1), 1998, pp. 163-170
Previous investigations in several systems have demonstrated that Rab3
family members redistribute to soluble fractions on fusion of secreto
ry granules with target plasma membranes. Rab proteins are then recycl
ed back onto mature secretory vesicles after reinternalization of the
membrane. Although this cycle is well established for Rab3, far less i
s known about redistribution of other Rab proteins during vesicle fusi
on and recycling. In the gastric parietal cell, Rab11a is associated w
ith H-K-ATPase-containing tubulovesicles, which fuse with the apical p
lasma membrane (secretory canaliculus) in response to agonists such as
histamine. We have analyzed distribution of Rab11a and other tubulove
sicle proteins in resting and histamine-stimulated rabbit parietal cel
ls. Stimulation of isolated gastric glands in the presence of 100 mu M
histamine and 100 mu M 3-isobutyl-1-methylxanthine did not cause a si
gnificant increase in soluble Rab11a. H-K-ATPase, Rab11a, Rab25, synta
xin 3, and SCAMPs increased immunoreactivity in stimulus-associated ve
sicles prepared from rabbits treated with histamine compared with thos
e from ranitidine-treated animals. The large GTPase dynamin was found
in both vesicle preparations, but there was no change in amount of imm
unoreactivity. Immunofluorescence staining of resting and histamine-st
imulated primary cultures of parietal cells demonstrated redistributio
n of H-K-ATPase and Rab11a to F-actin-rich canalicular membranes. Dyna
min was present on canalicular membranes in resting and stimulated cel
ls. These results indicate that Rab11a does not cycle off the membrane
during the process of tubulovesicle fusion with the secretory canalic
ulus. Thus Rab11a may remain associated with recycling apical membrane
vesicle populations.