Acidification of Intracellular Organelles

Glycoproteins of the lysosomal membrane.

“…Among the best characterized of these functions is acidification. Lysosomes lower their internal pH through the activity an an ATP-driven H ÷ pump that is mechanistically related to H ÷ pumps found in endosomes, coated vesicles, Golgi membranes, and acidic secretory organelles such as the chromaffin granule (5,32,33). Although the lysosomal H ÷-ATPase remains to be identified, it is conceivable that one (or more) of the antigens described here might be related to lysosomal acidification.…”

“…It remains to be determined whether either of these antigens is related to the lysosomal 1846 THE JOURNAL OF CELL BIOLOGY . VOLUME 100, 1985 H+-ATPase, which is mechanistically distinct from the mucosal K ÷, H+-ATPase (5,32,33).…”

“…However, unlike antibodies to lgp 100 and lgp80, Reggio et al's anti-100-kD antiserum displays detectable reactivity in Golgi cisternae by immunoperoxidase cytochemistry (17). It remains to be determined whether either of these antigens is related to the lysosomal H+-ATPase, which is mechanistically distinct from the mucosal K ÷, H+-ATPase (5,32,33).…”

“…Of particular interest in this regard, we have begun to characterize a series of monoclonal antibodies that were generated by immunization with highly purified bovine adrenal chromaffin granule membranes and that recognize four additional N-glycosylated lysosomal membrane proteins (150, 55, 30, and 20 kD) (manuscript in preparation). Since lysosomes and secretory chromaffin granules would be expected to share few (if any) functional activities aside from acidification (33), the recognized glycoproteins may be involved in the generation of transmembrane pH gradients. Reggio et al (17) recently identified a 100-kD antigen in rat liver lysosomal membrane an antibody to which reacted on Western blots with a putative H ÷, K÷-ATPase from porcine gastric mucosa.…”