The regulation of tyrosine kinase phosphorylation is critical for the growth and guidance of axons. Evidence suggests that the CAM-like receptor-tyrosine phosphatases (RPTPs) play key roles in the signaling processes underlying axon growth. This project tests the hypothesis that RPTPs, expressed on the surface of developing neurons regulate axon growth during embryogenesis, through the binding of specific ligands to their extracellular domains. The focus here is on 2 specific RPTPs -- CRYP-2 and PTP-deltadelta -- that are excellent candidates for involvement in the regulation of axon growth. Evidence implicating these two RPTPs includes structure, expression pattern, and preliminary analysis of function in vitro. The major questions concerning these RPTPs are: What are the regulatory ligands for CRYP-2 and PTP-delta?, and How are CRYP-2 and PTP-delta involved in axon growth? These questions will be addressed through correlation of expression of ligands for CRYP-2 and PTP-delta with expression of the RPTPs themselves, characterization of these ligands, and examination of the function of CRYP-2 and PTP-delta in axon growth, both in vitro and in vivo. There are three specific aims. First, potential regulatory ligands for the RPTPs will be localized, and identified through immunoprecipitation, affinity chromatography and expression cloning. Identification of ligands will allow key biochemical experiments on adhesive and signaling functions of these RPTPs. Second, the extracellular domains of the RPTPs will be used as regulators of axon growth and guidance in vitro, in an analysis of the mechanisms involved in this regulation. These results will provide detailed mechanistic evidence concerning how these RPTPs function. Finally, two different in vivo assay systems (retroviral expression of mutants and gene knockout) will be employed to assess the role of these RPTPs in neuronal development during embryogenesis. These assays will provide direct tests of the hypothesis that the specific PTPs under study are functionally linked to axon growth and guidance in vivo. The proposed experiments will move the field closer to a molecular understanding of the regulation of vertebrate axon growth. This understanding is critical for rational approaches to developmental disorders of the nervous system, as well as the problem of spinal cord regeneration.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS038920-03
Application #
6394174
Study Section
Special Emphasis Panel (ZRG1-MDCN-7 (01))
Program Officer
Mamounas, Laura
Project Start
1999-07-15
Project End
2003-06-30
Budget Start
2001-07-01
Budget End
2002-06-30
Support Year
3
Fiscal Year
2001
Total Cost
$272,410
Indirect Cost
Name
University of Miami School of Medicine
Department
Pharmacology
Type
Schools of Medicine
DUNS #
City
Miami
State
FL
Country
United States
Zip Code
33146
Tseng, Leinweih Andrew; Bixby, John L (2011) Interaction of an intracellular pentraxin with a BTB-Kelch protein is associated with ubiquitylation, aggregation and neuronal apoptosis. Mol Cell Neurosci 47:254-64
Kotani, Takenori; Murata, Yoji; Ohnishi, Hiroshi et al. (2010) Expression of PTPRO in the interneurons of adult mouse olfactory bulb. J Comp Neurol 518:119-36
Gonzalez-Brito, Manuel R; Bixby, John L (2009) Protein tyrosine phosphatase receptor type O regulates development and function of the sensory nervous system. Mol Cell Neurosci 42:458-65
Hower, Amy E; Beltran, Pedro J; Bixby, John L (2009) Dimerization of tyrosine phosphatase PTPRO decreases its activity and ability to inactivate TrkC. J Neurochem 110:1635-47
Gonzalez-Brito, Manuel R; Bixby, John L (2006) Differential activities in adhesion and neurite growth of fibronectin type III repeats in the PTP-delta extracellular domain. Int J Dev Neurosci 24:425-9
Chen, Bo; Bixby, John L (2005) Neuronal pentraxin with chromo domain (NPCD) is a novel class of protein expressed in multiple neuronal domains. J Comp Neurol 481:391-402
Chen, Bo; Bixby, John L (2005) A novel substrate of receptor tyrosine phosphatase PTPRO is required for nerve growth factor-induced process outgrowth. J Neurosci 25:880-8
Dimitropoulou, Anastasia; Bixby, John L (2005) Motor neurite outgrowth is selectively inhibited by cell surface MuSK and agrin. Mol Cell Neurosci 28:292-302
Stepanek, Laurie; Stoker, Andrew W; Stoeckli, Esther et al. (2005) Receptor tyrosine phosphatases guide vertebrate motor axons during development. J Neurosci 25:3813-23
Baerwald-de la Torre, Kristine; Winzen, Uwe; Halfter, Willi et al. (2004) Glycosaminoglycan-dependent and -independent inhibition of neurite outgrowth by agrin. J Neurochem 90:50-61

Showing the most recent 10 out of 16 publications