Differential binding of receptor protein tyrosine phosphatase type IIa family (RPTPσ/RPTPδ/LAR) to glycosaminoglycans

Monday, September 22, 2014 — Poster Session I
12:00 p.m. – 2:00 p.m.	FAES Academic Center	NHLBI	NEURO-21

Authors

• A.A. Morgan
• Y. Katagiri
• P. Yu
• N.J. Banayan
• R. Junka
• H.M. Geller

Abstract

Type IIa Receptor protein tyrosine phosphatases (RPTPs) have been shown to influence neural development and regeneration. Compelling evidence suggests that both heparan sulfate (HS) and chondroitin sulfate (CS) are ligands for RPTPσ, and LAR and express functional outputs of axonal growth promotion and inhibition, respectively. This effect was attributed to HS, but not to CS, inducing clustering of the extracellular region of RPTPσ. Here we show that all RPTP type IIa members (RPTPσ, RPTPδ, and LAR) display high affinity binding for heparin. Furthermore, CS-E and dermatan sulfate (DS) have similar nanomolar dissociation constants. However, we demonstrate differential contribution of FNIII domains required for high affinity binding to GAGs. In particular, RPTPσ binding to heparin was not completely abolished by the disruption of the Lys-loop. This led us to hypothesize and find that there is a greater contribution of the FN domain in binding to glycosaminoglycans than previously believed. Despite structural similarity amongst RPTPs, we conclude the presence of discrete bindings to GAGs. Also, our data indicate that clustering of the receptor may not explain the distinct biological functions of HS and CS.

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