CLAUSTRIN, AN ANTIADHESIVE NEURAL KERATAN SULFATE PROTEOGLYCAN, IS STRUCTURALLY RELATED TO MAP1B

Our laboratory has recently identified a keratan sulfate proteoglycan (KSPG), named claustrin, that inhibits neural cell adhesion and neurit e outgrowth in the chick nervous system. Antisera prepared against cla ustrin were used to screen a cDNA expression library from embryonic da y 9 chick brain. Initial characterization of positive cDNAs revealed a high degree of homology to the mouse MAP1B gene, although these cDNAs represent a 5' truncated fragment of MAP1B. Protein sequencing of thr ee peptides derived from a tryptic digest of purified, keratanase-trea ted claustrin also revealed strong homology to MAP1B, and confirmed th e authenticity of the 3.4 kb claustrin cDNA. To further determine the relationship between these two proteins, we used antibodies against MA P1B and KSPGs in immunoblotting and immunohistochemical studies. These studies demonstrated cross-reactivity between MAP1B and claustrin ant ibodies, and that monoclonal antibodies to cartilage keratan sulfate r eact with MAP1B in rat nervous tissue, and with claustrin in the chick nervous system. In addition, keratanase treatment of a taxol microtub ule fraction from chick or rat brain eliminated MAP1B, as detected by immunoblotting with the MAPS monoclonal antibody. These results sugges t that MAP1B and claustrin are highly related, if not identical, prote ins. (C) 1994 John Wiley and Sons, Inc.