Beta-dystroglycan: subcellular localisation in rat brain and detection of a novel immunologically related, postsynaptic density-enriched protein.

The distribution of a glycoprotein component of the muscle dystrophin complex, beta-dystroglycan, has been determined in subcellular fractions of adult rat forebrain. The results show that beta-dystroglycan is enriched in several membrane fractions, including synaptic membranes, but in marked contrast to dystrophin is not detectable in the postsynaptic density fraction. The antiserum also recognises a second molecular species of apparent molecular mass of 164 kDa which is highly enriched in the postsynaptic density fraction. Preabsorption of the antiserum with the antigen (a 22-mer peptide corresponding to the C-terminal sequence of rabbit skeletal muscle beta-dystroglycan) abolished reactivity against both beta-dystroglycan and the 164-kDa postsynaptic density-enriched protein, confirming that the two species are immunologically related. Enzymatic removal of N-linked oligosaccharide lowered the apparent molecular mass of beta-dystroglycan by 3 kDa but did not alter the mass of the 164-kDa species.