Identification of CRAM, a Novel unc-33 Gene Family Protein That Associates with CRMP3 and Protein-tyrosine Kinase(s) in the Developing Rat Brain

• Published in: The Journal of biological chemistry Vol. 275; no. 35; p. 27291
• Main Author: Inatome, R.
• Format: Journal Article
• Language: English
• Published: American Society for Biochemistry and Molecular Biology 01.09.2000
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M910126199

Four members of collapsin response mediator proteins (CRMPs) are thought to be involved in the semaphorin-induced growth cone collapse during neural development. Here we report the identification of a novel CRMP3-associated protein, designated CRAM for CR MP3- a ssociated m olecule, that belongs to the unc -33 gene family. The deduced amino acid sequence reveals that the CRAM gene encodes a protein of 563 amino acids, shows 57% identity with dihydropyrimidinase, and shows 50–51% identity with CRMPs. CRAM appears to form a large complex composed of CRMP3 and other unidentified proteins in vivo . Indeed, CRAM physically associates with CRMP3 when co-expressed in COS-7 cells. The expression of CRAM is brain-specific, is high in fetal and neonatal rat brain, and decreases to very low levels in adult brain. Moreover, CRAM expression is up-regulated during neuronal differentiation of embryonal carcinoma P19 and PC12 cells. Finally, immunoprecipitation analysis of rat brain extracts shows that CRAM is co-immunoprecipitated with proteins that contain protein-tyrosine kinase activity. Taken together, our results suggest that CRAM, which interacts with CRMP3 and protein-tyrosine kinase(s), is a new member of an emerging family of molecules that potentially mediate signals involved in the guidance and outgrowth of axons.