ICAAR, A NOVEL MEMBER OF A NEW FAMILY OF TRANSMEMBRANE, TYROSINE PHOSPHATASE-LIKE PROTEINS

We have isolated a cDNA from human foetal brain cDNA library which enc odes a putative transmembrane protein bearing an intracellular protein tyrosine phosphatase (PTPase) like domain. The PTPase Like domain con tains an alanine to aspartate amino acid change relative to other PTPa ses in the catalytic core domain. This amino acid change is found in o nly three other known proteins, islet cell autoantigens; human, murine and rat IA-2, murine IA 2b and its rat orthologue phogrin, which have a similar overall structure to ICAAR, and the recently identified X-l inked myotubular myopathy (MTMl) gene. ICAAR, IA-2 and IA 2b clearly r epresent a new family of PTP-like proteins for which catalytic activit y has yet to be demonstrated. An abundant ICAAR mRNA is detectable in the brain and pancreas but not in the other normal human tissues surve yed. We have localised ICAAR to human chromosome 7q36. (C) 1996 Academ ic Press, Inc.