WNK1 is involved in Nogo66 inhibition of OPC differentiation

LINGO-1 is a transmembrane receptor expressed primarily in the central nervous system (CNS) and plays an important role in myelination. Recent studies have indicated that it is also involved in oligodendrocyte precursor cell (OPC) survival and differentiation; however, the downstream signaling pathway underlying OPC development is unknown. In our previous study, we found that LINGO-1 is associated with WNK1 in mediating Nogo-induced neurite extension inhibition by RhoA activation. In an effort to identify the role of LINGO-1-WNK1 in OPCs, we first confirmed that WNK1 is also expressed in OPCs and co-localized with LINGO-1, which suppresses WNK1 expression by RNA interference-attenuated Nogo66-induced inhibition of OPC differentiation. Furthermore, we mapped the WNK1 kinase domain using several fragmented peptides to identify the key region of interaction with LINGO-1. We found that a sequence corresponding to the D6 peptide is necessary for the interaction. Finally, we found that using the TAT-D6 peptide to introduce D6 peptide into primary cultured OPC inhibits the association between LINGO-1 and WNK1 and significantly attenuates Nogo66-induced inhibition of OPC differentiation. Taken together, our results show that WNK1, via a specific region on WNK1 kinase domain, interacts with LINGO-1, thus mediating Nogo66-inhibited OPC differentiation.