Canadian Health&Care; Mall

Some isoforms could serve as a possible alternative mechanism for the active role played by the predominant one in the V-ATPase holoenzyme. Mutations of some subunits of the V-ATPase, including Bl and a4, are linked to renal distal tubular acidosis and deafness. Our finding that a4 and Bl are highly expressed in narrow and clear cells of the epididymis raised the possibility that fertility might be altered in patients harboring these mutations. Long-term clinical follow-up of these young patients will be required to address this question. However, mice lacking the Bl subunit are not infertile (Karen E. Finberg, personal communication and our observations), indicating that their epididymal luminal acidification, which is necessary for sperm maturation and storage, is not critically impaired. These studies suggest that another B isoform, possibly B2, can compensate for the lack of Bl to maintain active proton secretion. Similarly, al might represent a possible backup or alternative mechanism for the active role played by the a4 isoform in luminal proton secretion in clear cells.