Retina-specifically Expressed Novel Subtypes of Bovine Cyclophilin

Abstract

The Drosophila ninaA gene encodes photoreceptorspecific cyclophilin thought to play a critical role in rhodopsin folding or transport during its synthesis or maturation in the most abundant subclass of photoreceptors. Cyclophilins comprise a highly conserved family of proteins which are the primary targets of the potent immunosuppressive drug, cyclosporin A (CsA), and which display peptidyl prolyl cis-trans-isomerase (PPIase) activity. In an attempt to identify mammalian cyclophilins with properties similar to the NinaA protein, a probe derived from the ninaA cDNA was used to screen bovine retinal cDNA libraries. The screen identified two major alternatively spliced forms of cDNA that would encode proteins containing a region of high homology to other cyclophilins and that are expressed specifically in the retina. These proteins represent a new class of cyclophilins with novel structural features and greatly reduced PPIase and CsA binding activities in comparison to other known cyclophilins. Tissue in situ hybridization and immunolocalization of the proteins showed that the RNA and protein products are expressed in photoreceptors as well as other retinal neurons. However, among photoreceptors, the proteins are found predominantly in cones. Thus, mammalian retinas do contain cyclophilins that are retina-specifically and photoreceptor class-preferentially expressed. The results suggest that, in cones, the main function of these proteins is, like the NinaA protein, to facilitate proper folding or intracellular transport of opsins.

The Peptidyl-prolyl Isomerase Domain of the CyP-40 Cyclophilin Homolog Cpr7 Is Not Required to Support Growth or Glucocorticoid Receptor Activity in Saccharomyces cerevisiae

“…Using a standard assay (35), isomerase activity was detected with the related cyclophilin Cpr6 2 (30,36) but not with Cpr7 (30). 2 Similar observations have been reported for the bovine cyclophilin RanBP2, which showed only marginal isomerase activity in vitro (37). It is possible that the isomerase activity of Cpr7 was missed because the peptide substrate used in the assay does not sufficiently mimic natural Cpr7 substrates.…”

Failed export of the adrenocorticotrophin receptor from the endoplasmic reticulum in non-adrenal cells: evidence in support of a requirement for a specific adrenal accessory factor

“…ninaA mutants result in retention of rhodopsin in the endoplasmic reticulum (Baker et al 1994). Mammalian homologues of ninaA have been identified and these are expressed in a tissue-specific manner in retinal cells (Ferreira et al 1995). Caenorhabditis elegans olfactory receptors are localized to the cilia of olfactory neurones under the direction of the odr-4 and odr-8 genes.…”

A Cytosolic, Gαq- and βγ-insensitive Splice Variant of Phospholipase C-β4

“…Recent results obtained from in situ hybridizations of rat brain tissue sections and from a mouse that lacks PLC-␤4 suggest that PLC-␤4 may play a significant role in mammalian visual processing (31,41). In our study, we isolated a novel splice variant of rat PLC-␤4 and named it PLC-␤4b.…”