Fumio Nakamura
   Department   School of Medicine, School of Medicine
   Position   Professor and Division head
Language English
Title Hyperphosphorylation of SIRP alpha in PTP delta knockout mouse brains
Conference The 42nd Annual Meeting of the Japan Neuroscience Society
Conference Type Nationwide Conferences
Presentation Type Poster notice
Lecture Type General
Publisher and common publisherMiyu Wakatsuki, Fumio Nakamura
Date 2019/07/25
Venue
(city and name of the country)
Niihgata, Japan
Summary Protein tyrosine phosphatase delta (PTP delta) is one of vertebrate Leukocyte common antigen-related (LAR) class PTPs. We previously reported that PTP delta is involved in the development of cortical pyramidal neurons through the activation of Fyn tyrosine kinase. However, in vivo substrates of PTP delta are largely unknown. As we observed hyperphosphorylated proteins in PTP delta knockout mouse brains by immunoblotting with anti-phosphotyrosine (pY) antibody, we carried out phospho-proteomics analysis of the knockout and wild-type brains (postnatal day 25). Among the identified proteins, Signal Regulatory Protein alpha (SIRP alpha) gave the strongest phosphorylated ratio of knockout to wild-type. We then examined the phosphorylation of SIRP alpha in mouse brains (postnatal day 22) using antibodies against phosphotyrosine (pY), SIRP alpha, and phosphorylated Tyr501 in SIRP alpha (pY501). Combination of SIRP alpha-immunoprecipitation and pY-blotting as well as anti-pY501 immunoblotting revealed the hyperphosphorylation of SIRP alpha in the knockouts. We next examined immunohistochemistry. Almost entire CNS regions were immunostained with anti-pY antibody in both genotypes, however, the signal was stronger in the knockout sections than in wild-type. Cortical layers from Ⅱ to V, reticular thalamic nucleus, and subthalamic nuclei were hyperphosphorylated in the knockouts. Phospho-Y501 SIRP alpha immunostaining revealed that in the knockout sections, olfactory bundle, cortical II and III layers, striate body, fimbria, corpus callosum, reticular thalamic nucleus, ethmoid thalamic nucleus, and pyramidal tract were hyperphosphorylated. In addition, rostral migratory stream (RMS) was strongly immunostained with pY501 SIRP alpha in both genotypes. SIRP alpha-hyperphosphorylated regions in the knockouts partially correlated with the regions expressing PTP delta in wild-type including neocortex and thalamic reticular nucleus. This suggests that SIRP alpha may be one of the endogenous substrates of PTP delta.