HIGH-AFFINITY BINDING AND OVERLAPPING LOCALIZATION OF NEUROCAN AND PHOSPHACAN PROTEIN-TYROSINE PHOSPHATASE-ZETA BETA WITH TENASCIN-R, AMPHOTERIN, AND THE HEPARIN-BINDING GROWTH-ASSOCIATED MOLECULE/

Citation
P. Milev et al., HIGH-AFFINITY BINDING AND OVERLAPPING LOCALIZATION OF NEUROCAN AND PHOSPHACAN PROTEIN-TYROSINE PHOSPHATASE-ZETA BETA WITH TENASCIN-R, AMPHOTERIN, AND THE HEPARIN-BINDING GROWTH-ASSOCIATED MOLECULE/, The Journal of biological chemistry, 273(12), 1998, pp. 6998-7005
Citations number
40
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Biology
ISSN journal
0021-9258
Volume
273
Issue
12
Year of publication
1998
Pages
6998 - 7005
Database
ISI
SICI code
0021-9258(1998)273:12<6998:HBAOLO>2.0.ZU;2-H
Abstract
We have studied the interactions of the nervous tissue-specific chondr oitin sulfate proteoglycans neurocan and phosphacan with the extracell ular matrix protein tenascin-a and two heparin-binding proteins, ampho terin and the heparin-binding growth-associated molecule (HB-GAM), usi ng a radioligand binding assay, Both proteoglycans show saturable, hig h affinity binding to tenascin-R with apparent dissociation constants in the 2-7 nM range, Binding is reversible, inhibited in the presence of unlabeled proteoglycan, and increased by similar to 60% following c hondroitinase treatment of the proteoglycans, indicating that the inte ractions are mediated via the core (glyco)proteins rather than by the glycosaminoglycan chains, which may in fact partially shield the bindi ng sites, In contrast to their interactions with tenascin-C, in which binding was decreased by similar to 75% in the absence of calcium, bin ding of phosphacan to tenascin-R was not affected by the absence of di valent cations in the binding buffer, although there was a small but s ignificant decrease in the binding of neurocan, Neurocan and phosphaca n are also high affinity ligands of amphoterin and HB-GAM (K-d = 0.3-8 nM), two heparin-binding proteins that are developmentally regulated in brain and functionally involved in neurite outgrowth, The chondroit in sulfate chains on neurocan and phosphacan account for at least 80% of their binding to amphoterin and HB-GAM. The presence of amphoterin also produces a 5-fold increase in phosphacan binding to the neural ce ll adhesion molecule contactin, Immunocytochemical studies showed an o verlapping localization of the proteoglycans and their ligands in the embryonic and postnatal brain, retina, and spinal cord, These studies have therefore revealed differences in the interactions of neurocan an d phosphacan with the two major members of the tenascin family of extr acellular matrix proteins, and also suggest that chondroitin sulfate p roteoglycans play an important role in the binding and/or presentation of differentiation factors in the developing central nervous system.