The extracellular matrix in the mouse brain: Its reactions to endo-alpha-N-acetylgalactosaminidase and certain other enzymes

As our previous studies have indicated, the cingulate cortex of the adult m ouse brain contains many neurons with rich cell surface glycoproteins which are linked by collagenous ligands to perineuronal proteoglycans. The prese nt study demonstrated that exclusive incubation with endo-alpha-N-acetylgal actosaminidase abolished the lectin Vicia villosa or Wisteria floribunda ag glutinin (VVA or WFA) labeling of the nerve cell surface glycoproteins, whi le it neither interfered with the cationic iron colloid or aldehyde fuchsin stainings of the perineuronal proteoglycans nor abolished the Gomori's amm oniacal silver impregnation of the collagenous ligands. Double incubations with endo-alpha-N-acetylgalactosaminidase and collagenase did not eliminate the lectin VVA or WFA labeling of the nerve cell surface glycoproteins, th ough they did eliminate the cationic iron colloid and aldehyde fuchsin stai nings of the perineuronal proteoglycans as well as the Gomori's ammoniacal silver impregnation of the collagenous ligands. Triple incubations with end o-alpha-N-acetylgalactosaminidase, collagenase, and endo-alpha-N-acetylgala ctosaminidase abolished the lectin VVA or WFA labeling of the nerve cell su rface glycoproteins, and also eliminated the cationic iron colloid and alde hyde fuchsin stainings of the perineuronal proteoglycans and the Gomori's a mmoniacal silver impregnation of the collagenous ligands. These findings in dicate that the nerve cell surface glycoproteins or their terminal N-acetyl galactosamines are digested by endo-alpha-N-acetylgalactosaminidase; these galactosamines associated with the collagenous ligands or perineuronal prot eoglycans are not digested by endo-alpha-N-acetyl-galactosaminidase; and th e terminal N-acetylgalactosamines newly exposed by collagenase incubation a re digested by this galactosaminidase. It was further demonstrated that hya luronidase incubation neither digests the collagenous ligands nor revives t he lectin VVA or WFA labeling of the nerve cell surface proteoglycans.