B. Vanhille et al., HETEROGENEITY OF VACUOLAR H-ATPASE - DIFFERENTIAL EXPRESSION OF 2 HUMAN SUBUNIT B-ISOFORMS(), Biochemical journal, 303, 1994, pp. 191-198
The catalytic domain of the vacuolar proton ATPase is composed of a he
xamer of three A subunits and three B subunits. Here we describe the c
loning and characterization of a cDNA isoform of subunit B, HO57, from
an osteoclastoma cDNA library. HO57 is represented by three species o
f mRNA of 1.6, 2.6 and 2.8 kb and is expressed at low levels in a rang
e of human tissues, but at significantly higher levels in brain, kidne
y and osteoclastoma, and is probably an ubiquitously expressed isoform
. In contrast, the kidney-specific isoform has an mRNA of 2kb and is s
pecifically expressed al high levels only in kidney and, at a lower le
vel, in placenta. Thus the HO57 isoform is integral to the vacuolar AT
Pase found in the general secretory system of all cells as well as in
vacuolar-ATPase-rich sources such as neurones and osteoclasts, whereas
both the kidney-specific isoform and HO57 are highly expressed in the
kidney. Furthermore, we show by in situ hybridization that HO57 is th
e only isoform that is exclusively and highly expressed by osteoclasts
.