Striatal enriched phosphatase 61 dephosphorylates Fyn at phosphotyrosine 420.
A family of protein tyrosine phosphatases enriched within the central nervous system called striatal enriched phosphatase (STEP) has been implicated in the regulation of the N-methyl-d-aspartate receptor. STEP(61), a membrane-associated isoform located in the postsynaptic densities (PSDs) of striatal neurons, contains two transmembrane domains, two proline-rich domains, and a kinase-interacting motif. This study demonstrates that STEP(61) associates with Fyn, a member of the Src family kinases that is also enriched in PSDs. By using human embryonic kidney 293 cells for co-transfection, we determined that a substrate-trapping variant (STEP(61) CS) binds to Fyn but not to other members of the Src family present in PSDs. In a complementary experiment, myc-tagged Fyn immunoprecipitates STEP(61) CS. STEP(61) binds to Fyn through one of its proline-rich domains and the kinase-interacting motif domain, whereas Fyn binds to STEP(61) through its Src homology 2 domain and the unique N-terminal domain. STEP(61) CS pulls down Fyn when the Tyr(420) site is phosphorylated. In vitro, wild-type STEP(61) dephosphorylates Fyn at Tyr(420) but not at Tyr(531). These results suggest that STEP regulates the activity of Fyn by specifically dephosphorylating the regulatory Tyr(420) and may be one mechanism by which Fyn activity is decreased within PSDs.
Nguyen
Tri-Hung
TH
Child Study Center, Yale University School of Medicine, New Haven, Connecticut 06520, USA. tnguyen@lumicyte.com
Liu
Jian
J
Lombroso
Paul J
PJ
D000818:Animals; D003342:Corpus Striatum / Q000201:enzymology*; D005260:Female; D009474:Neurons / Q000201:enzymology*; D019000:Phosphotyrosine / Q000378:metabolism*; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D054558:Protein Tyrosine Phosphatases, Non-Receptor; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051076:Proto-Oncogene Proteins c-fyn; D051381:Rats; D020318:Rats, Long-Evans
D011518:Proto-Oncogene Proteins; D019000:Phosphotyrosine; D011505:Protein-Tyrosine Kinases; C494961:Fyn protein, rat; D051076:Proto-Oncogene Proteins c-fyn; C489930:PTPN5 protein, human; D017027:Protein Tyrosine Phosphatases; D054558:Protein Tyrosine Phosphatases, Non-Receptor; C489931:Ptpn5 protein, rat