Cloning of human Ca2+ homoeostasis endoplasmic reticulum protein (CHERP): regulated expression of antisense cDNA depletes CHERP, inhibits intracellular Ca2+ mobilization and decreases cell proliferation

A monoclonal antibody which blocks InsP(3)-induced Ca2+ release from isolat ed endoplasmic reticulum was used to isolate a novel 4.0 kb cDNA from a hum an erythroleukaemia (HEL) cell cDNA expression library. A corresponding mRN A transcript of approx. 4.2 kb was present in all human cell lines and tiss ues examined, but cardiac and skeletal muscle had an additional transcript of 6.4 kb. The identification in GenBank(R) of homologous expressed sequenc e tags from many tissues and organisms suggests that the gene is ubiquitous ly expressed in higher eukaryotes. The gene was mapped to human chromosome 19p13.1. The cDNA predicts a 100 kDa protein, designated Ca2+ homoeostasis endoplasmic reticulum protein (CHERP), with two putative transmembrane doma ins, multiple consensus phosphorylation sites, a polyglutamine tract of 12 repeats and regions of imperfect tryptophan and histadine octa- and nona-pe ptide repeats. In vitro translation of the full-length cDNA produced protei ns of M, 128000 and 100000, corresponding to protein bands detected by West ern blotting of many cell types. CHERP was co-localized in HEL cells with t he InsP(3) receptor by two-colour immunofluorescence. Transfection of HEL c ells with antisense cDNA led to an 80 % decline in CHERP within 5 days of a ntisense induction, with markedly decreased intracellular Ca2+ mobilization by thrombin, decreased DNA synthesis and growth arrest, indicating that th e protein has an important function in Ca2+ homoeostasis, growth and prolif eration.