Functional analysis of protein tyrosine phosphatase in the formation of retinotectal projection

• Project/Area Number: 17500243
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Nerve anatomy/Neuropathology
• Research Institution: National Institute for Basic Biology
• Principal Investigator: SHINTANI Takafumi National Institute for Basic Biology, Molecular Neurobiology, Assistant professor, 統合神経生物学研究部門, 助教 (10312208)
• Project Period (FY): 2005 – 2006
• Project Status: Completed (Fiscal Year 2006)
• Budget Amount: ¥3,000,000 (Direct Cost: ¥3,000,000); Fiscal Year 2006: ¥1,300,000 (Direct Cost: ¥1,300,000); Fiscal Year 2005: ¥1,700,000 (Direct Cost: ¥1,700,000)
• Keywords: retina / tectum / retinal axon / projection / protein phosphatase / protein kinase / tyrosine phosphorylation / dephosphorylation

Research Abstract

Eph receptors are the largest family of receptor-type tyrosine kinases (RTKs) and are classified into two groups, A-type (EphAs) and B-type (EphBs)^1. The Eph receptors are involved in numerous events such as cell movements, axonal guidance, formation of synapses, maintenance of synaptic plasticity, organization of cell boundaries, formation of the cardiovasculature system and carcinogenesis^2. Interaction of the Eph receptors with their ligands, the ephrins, requires cell-cell contact in vivo because both the receptor and the ligand are membrane-bound. Although there exist exceptions^<3,4>, EphA receptors preferentially bind the ephrin-As, which are attached to the plasma membrane through a glycosylphosphatidylinositol (GPI) anchor, and EphB receptors preferentially bind the transmembrane ephrin-Bs. Upon binding the ephrin ligands, Eph receptors are autophosphorylated at several tyrosine residues and subsequently activate signaling cascades downstream. However, protein tyrosine phosph atases (PTPs) responsible for the negative regulation of Eph have not been elucidated. Here, I identified protein tyrosine phosphatase receptor type O (Ptpro) as a PTP that dephosphorylates Eph receptors as substrates. In mammalian two-hybrid and immunoprecipitation assays, a substrate-trapping mutant of Ptpro formed stable complexes with EphA4 and EphB2 receptors. In vitro assays using GST-fused forms of Ptpro showed direct dephosphorylation of Eph receptors by Ptpro. Experiments with point-mutant constructs of EphA4 and EphB2 as well as those with phosphopeptides revealed that Ptpro dephosphorylates a phosphotyrosine residue conserved in the juxtamembrane region, which is required for the activation and signal transmission of Eph receptors. Using the chick retinotectal projection system, I show that Ptpro controls the sensitivity of retinal axons to ephrins and thereby has a crucial role in the establishment of topographic projections. My findings explain the molecular mechanism that determines the threshold of the response of Eph receptors to ephrins in vivo.

Research Products

• [Journal Article] Eph receptors are negatively controlled by protein tyrosine phosphatase receptor type O. (2006)
  • Author(s): Shintani, T., Ihara, M., Sakuta, H., Takahashi, H., Watakabe, I., Noda, M.
  • Journal Title: Nature Neuroscience 9 Pages: 761-769
  • Description: 「研究成果報告書概要(和文)」より
• [Journal Article] Role of bone morphogenic protein 2 in retinal patterning and retinotectal projection. (2006)
  • Author(s): Sakuta, H., Takahashi, H., Shintani, T., Etani, K., Aoshima, A., Noda, M.
  • Journal Title: Journal of Neuroscience 26 Pages: 10868-10878
  • Description: 「研究成果報告書概要(和文)」より
• [Journal Article] Upregulation of retinal transglutaminase during the axonal elongation stage of goldfish optic nerve regeneration. (2006)
  • Author(s): Sugitani, K., Matsunaga, T., Koriyama, Y., Shintani, T., Nakamura, T., Noda, M., Kato, S.
  • Journal Title: Neuroscience 142 Pages: 1081-1092
  • Description: 「研究成果報告書概要(和文)」より
• [Journal Article] Role of bone morphogenic protein 2 in retinal patterning and retinotectal projection (2006)
  • Author(s): Sakuta, H., Takahashi, H., Shintani, T., Etani, K, Aoshima, A., Noda, M.
  • Journal Title: Journal of Neuroscience 26 Pages: 10868-10878
  • Description: 「研究成果報告書概要(欧文)」より
• [Journal Article] Upregulation of retinal transglutaminase during the axonal elongation stage of goldfish optic nerve regeneration (2006)
  • Author(s): Sugitani, K, Matsunaga, T., Koriyama, Y., Shintani, T., Nakamura, T., Noda, M, Kato, S
  • Journal Title: Neuroscience 142 Pages: 1081-1092
  • Description: 「研究成果報告書概要(欧文)」より
• [Journal Article] Eph receptors are negatively controlled by protein tyrosine phosphatase receptor type O. (2006)
  • Author(s): Shintani, T., Ihara, M., Sakuta, H., Takahashi, H., Watakabe, I., Noda,M.
  • Journal Title: Nature Neuroscience 9 Pages: 761-769
• [Journal Article] Role of bone morphogenic protein 2 in retinal patterning and retinotectal projection. (2006)
  • Author(s): Sakuta, H., Takahashi, H., Shintani, T., Etani, K., Aoshima, A., Noda,M.
  • Journal Title: Journal of Neuroscience 26 Pages: 10868-10878