THE UBIQUITOUS VA68 ISOFORM OF SUBUNIT-A OF THE VACUOLAR H-ATPASE IS HIGHLY EXPRESSED IN HUMAN OSTEOCLASTS()

The 67-kDa subunit A of the vacuolar-type H+-ATPase carries the high a ffinity ATP binding site and together with the 57-kDa subunit B forms the catalytic domain. Two isoforms of subunit A, VA68 and HO68, were c loned from an osteoclastoma cDNA library. We have analyzed their respe ctive expression patterns in different tissues by RNAse A protection a nd in situ hybridization. The HO68 isoform was found to be present onl y in the tumor originally used to construct the cDNA library, whereas the ubiquitous VA68 RNA isoform was detected in large osteoclastic cel ls, as well as in brain and kidney, by RNAse protection assay. Further more, we localised the strong signal observed in osteoclastoma RNA to the large osteoclastic cells by in situ hybridisation. These findings suggest that the subunit A highly expressed in human osteoclasts is th e ubiquitous isoform, VA68. (C) 1995 Academic Press, Inc.