Jj. Crouch et Ba. Schulte, IDENTIFICATION AND CLONING OF SITE-C SPLICE VARIANTS OF PLASMA-MEMBRANE CA-ATPASE IN THE GERBIL COCHLEA, Hearing research, 101(1-2), 1996, pp. 55-61
Plasma membrane Ca-ATPase (PMCA) gene products were identified in the
gerbil cochlea by reverse-transcription polymerase chain reaction (RT-
PCR). Cochlear cDNA was amplified using PMCA isoform-specific primers
from splice site C, the calmodulin binding domain. PCR products were c
loned and sequenced. The putative housekeeping PMCA genes, 1b and 4b,
as expected, were present in the gerbil cochlea and shared 98.6 and 10
0% amino acid homology with published rat sequences, at splice site C,
respectively. PMCA2b, 3a and 3b splice variants also were detected in
cochlear cDNAs and shared 95, 94.3 and 98% amino acid homology with t
heir rat counterparts. PMCA isoforms 2 and 3 have been shown to occur
in highly specialized tissues, such as muscle and brain, that require
finely tuned regulation of intracellular free Ca2+ levels. The presenc
e of several isoforms and splice variants of PMCA in the cochlea most
probably reflects their differential expression among the several cell
types that have been shown to contain immunoreactive PMCA. This sugge
sts that the cochlea has developed complex mechanisms that finely tune
intracellular Ca2+ levels in different highly specialized cell types.