CLONING OF PCPTP1-CE ENCODING PROTEIN-TYROSINE-PHOSPHATASE FROM THE RAT CEREBELLUM AND ITS RESTRICTED EXPRESSION IN PURKINJE-CELLS

Recently, cDNAs encoding brain-specific transmembrane-type protein tyr osine phosphatases (PTPs) with single catalytic domain have been clone d. These include PC12-PTP, PCPTP1, PTPBR7, and PTP-SL, whose cytoplasm ic domains had high similarity to STEP, a brain-specific nontransmembr ane-type PTP. Based on the high similarity and expression pattern, PCP TP1 seems to be identical with PC12-PTP1 and to be the rat homologue o f murine PTPBR7. Here, we report the molecular cloning and expression profile of PCPTP1-Ce, a variant of PCPTP1. Both PCPTP1 mRNA and PCPTP1 -Ce mRNA seem to be derived from a single common region gene. Nucleoti de and deduced amino acid sequence comparison between PCPTP1-Ce and PC PTP1 revealed that the predicted protein product of PCPTP1-Ce is ident ical with that translated from the third initiation methionine of the longest ORF of PCPTP1, and that these two clones differ in the 5'-untr anslated sequences. Northern blot analyses with specific probes for PC PTP1 and PCPTP1-Ce confirmed our previous observation that PCPTP1-Ce m RNA was almost exclusively expressed in the cerebellum, whereas PCPTP1 was widely expressed in various brain regions dissected including cer ebellum. In situ hybridization study demonstrated that PCPTP1-Ce mRNA was exclusively expressed in Purkinje cells of the cerebellum. In cont rast, PCPTP1 mRNA was predominantly expressed in granule cells and les s in Purkinje cells. Moreover, immunohistochemical analysis using an a ffinity-purified polyclonal antibody raised against the cytoplasmic re gion of PCPTP1/PCPTP1-Ce demonstrated that Purkinje cells were strongl y immunostained, whereas granule cells were stained only faintly in th e cerebellum. These observations clearly demonstrated that PCPTP1-Ce m RNA and its protein products are expressed in Purkinje cells and sugge st that PCPTP1-Ce may play an important role in Purkinje cell function in the rat cerebellum. (C) 1998 Elsevier Science B.V. All rights rese rved.