Receptor tyrosine phosphatase β is expressed in the form of proteoglycan and binds to the extracellular matrix protein tenascin

The extracellular domain of receptor type protein tyrosine phosphatase β (RPTPβ) exhibits striking sequence similarity with a soluble, rat brain chondroitin sulfate proteoglycan (3F8 PG). Immunoprecipitation experiments of cells transfected with RPTPβ expression vector and metabolically labeled with [³⁵S]sulfate and [³⁵S]methionine indicate that the transmembrane form of RPTPβ is indeed a chondroitin sulfate proteoglycan. The 3F8 PG is therefore a variant form composed of the entire extracellular domain of RPTPβ probably generated by alternative RNA splicing. Previous immunohistochemical studies indicated that both RPTPβ and the extracellular matrix protein tenascin are localized in similar regions of the central nervous system. We have performed co-aggregation assays with red and green Covaspheres coated with tenascin and 3F8 PG, respectively, showing that the extracellular domain of RPTPβ (3F8 PG) binds specifically to tenascin. The interaction between a receptor tyrosine phosphatase and an extracellular matrix protein may have a role in development of the mammalian central nervous system.