Striatal‐enriched protein tyrosine phosphatase regulates the PTPα/Fyn signaling pathway

Abstract

The tyrosine kinase Fyn has two regulatory tyrosine residues that when phosphorylated either activate (Tyr420) or inhibit (Tyr531) Fyn activity. Within the central nervous system, two protein tyrosine phosphatases (PTPs) target these regulatory tyrosines in Fyn. PTPα dephosphorylates Tyr531 and activates Fyn, while STEP (STriatal-Enriched protein tyrosine Phosphatase) dephosphorylates Tyr420 and inactivates Fyn. Thus, PTPα and STEP have opposing functions in the regulation of Fyn; however, whether there is cross talk between these two PTPs remains unclear. Here, we used molecular techniques in primary neuronal cultures and in vivo to demonstrate that STEP negatively regulates PTPα by directly dephosphorylating PTPα at its regulatory Tyr789. Dephosphorylation of Tyr789 prevents the translocation of PTPα to synaptic membranes, blocking its ability to interact with and activate Fyn. Genetic or pharmacologic reduction of STEP61 activity increased the phosphorylation of PTPα at Tyr789, as well as increased translocation of PTPα to synaptic membranes. Activation of PTPα and Fyn and trafficking of GluN2B to synaptic membranes are necessary for ethanol intake behaviors in rodents. We tested the functional significance of STEP61 in this signaling pathway by ethanol administration to primary cultures as well as in vivo, and demonstrated that the inactivation of STEP61 by ethanol leads to the activation of PTPα, its translocation to synaptic membranes, and the activation of Fyn. These findings indicate a novel mechanism by which STEP61 regulates PTPα and suggest that STEP and PTPα coordinate the regulation of Fyn.

Inhibition of the tyrosine phosphatase STEP61 restores BDNF expression and reverses motor and cognitive deficits in phencyclidine-treated mice

“…Lentivirus-based STEP shRNA (LV-STEP) was validated as described [31, 40, 41]. Rat cortical cultures were infected with LV-STEP or a luciferase control at DIV 7 for 7 days.…”

“…Rat cortical cultures were infected with LV-STEP or a luciferase control at DIV 7 for 7 days. A recombinant adeno-associated virus of mixed serotype 1/2 (AAV1/2) was custom made (GeneDetect LTD, Auckland, New Zealand), and validated as described [31]. At DIV 5, STEP KO mouse cortical neurons were infected with AAV1/2-STEP 61 or AAV1/2-control vector for 7 days prior to PCP exposure.…”

Molecular mechanisms underlying alcohol-drinking behaviours

“…In fact, the requirement of PKA for alcohol-mediated activation of FYN was first reported in hippocampal slices 31 . Alcohol-mediated inhibition of STEP also enables the activation of protein-tyrosine phosphatase-α (PTPα) 32 , which is required for the activation of FYN 33 . Indeed, excessive alcohol intake (20%IA2BC model) increases the interaction between FYN and PTPα, which in turn contributes to the sustained activation of the kinase 30 .…”

STEP activation by Gαq coupled GPCRs opposes Src regulation of NMDA receptors containing the GluN2A subunit

“…Previous studies have shown that Fyn, but not Src, is a STEP substrate3234. Evidence also suggests an interaction between STEP 61 and GluN2A in heterologous cell lines35.…”

“…To confirm the parallel stimulation of Src and STEP activity by M1Rs and consequent change in GluN2A tyrosine phosphorylation, we used Western blotting to examine: (1) Phosphorylation of STEP at Ser221 within the substrate binding domain28. Phosphorylation of this site sterically prevents the association of STEP with substrates, resulting in an increase in Tyr phosphorylation of these substrates29303132. (2) Phosphorylation of Src at Tyr416.…”