Synaptojanin 2, a novel synaptojanin isoform with a distinct targeting domain and expression pattern

摘要: Synaptojanin (synaptojanin 1) is a recently identified inositol 5′-phosphatase, which highly enriched in nerve terminals and implicated synaptic vesicle recycling. It composed of three domains: an amino-terminal SacI homology region, central 5′-phosphatase carboxyl-terminal proline-rich region. We have now characterized novel form synaptojanin, synaptojanin 2, has broader tissue distribution. 2 cDNA from rat brain library encodes protein 1,248 amino acids with predictedM r 138,268. The two isoforms share 57.2 53.8% acid identity their phosphatase domains, respectively. In marked contrast, regions bear little homology. Expression COS7 cells produced 140-kDa actvity. Protein binding assays demonstrated that among the major src 3-proteins known to bind region 1, Grb2, amphiphysin, members SH3p4/8/13 family, only Grb2 bound 2. Furthermore, subcellular fractionation studies transfected Chinese hamster ovary revealed was predominantly associated particulate fraction while 1 mainly localized soluble fraction. This observation suggests synaptojanins are different protein-protein interactions direct compartments. Our results demonstrate presence family synaptojanin-type 5′-phosphatases distributions, may be involved distinct membrane trafficking signal transduction pathways mammalian cells.