The receptor protein tyrosine phosphatase LAR promotes R7 photoreceptor axon targeting by a phosphatase-independent signaling mechanism
- Kimmel Center for Biology and Medicine of the Skirball Institute and Department of Cell Biology, New York University School of Medicine, 540 First Avenue, New York, NY 10016
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Edited by Trudi Schupbach, Princeton University, Princeton, NJ, and approved September 30, 2009 (received for review April 10, 2009)
Abstract
Receptor protein tyrosine phosphatases (RPTPs) control many aspects of nervous system development. At the Drosophila neuromuscular junction (NMJ), regulation of synapse growth and maturation by the RPTP LAR depends on catalytic phosphatase activity and on the extracellular ligands Syndecan and Dally-like. We show here that the function of LAR in controlling R7 photoreceptor axon targeting in the visual system differs in several respects. The extracellular domain of LAR important for this process is distinct from the domains known to bind Syndecan and Dally-like, suggesting the involvement of a different ligand. R7 targeting does not require LAR phosphatase activity, but instead depends on the phosphatase activity of another RPTP, PTP69D. In addition, a mutation that prevents dimerization of the intracellular domain of LAR interferes with its ability to promote R7 targeting, although it does not disrupt phosphatase activity or neuromuscular synapse growth. We propose that LAR function in R7 is independent of its phosphatase activity, but requires structural features that allow dimerization and may promote the assembly of downstream effectors.
Footnotes
- 1To whom correspondence should be addressed. E-mail: jessica.treisman{at}med.nyu.edu
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Author contributions: K.H. and J.E.T. designed research; K.H. performed research; K.H. and J.E.T. analyzed data; and K.H. and J.E.T. wrote the paper.
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The authors declare no conflict of interest.
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This article is a PNAS Direct Submission.
