Pseudophosphatase MK‐STYX regulates neurite outgrowth and alters the morphology of primary neurons

Abstract

Mitogen‐activated protein kinases (MAPKs) are essential players in important neuronal signaling pathways including neuronal development, plasticity, survival, learning, and memory. The inactivation of MAPKs is tightly controlled by MAPK phosphatases (MKPs), which also are important regulators of these neuronal processes. There is compelling evidence that a unique catalytically inactive member of the MKP family, MK‐STYX (mitogen activated kinase phosphoserine/threonine/tyrosine binding protein), is a regulator in neuronal processes such as neurite outgrowth. We previously reported that the MK‐STYX dramatically increases the number of primary neurites in rat pheochromocytoma (PC‐12) cells through the RhoA signaling pathway. MK‐STYX decreases RhoA activation, whereas knockdown of MK‐STYX increases RhoA activation. Furthermore, MK‐STYX increases phosphorylation of cofilin, a RhoA downstream effector, whereas phosphorylated cofilin decreases when MK‐STYX is knocked down with shRNA. Throughout the course of these experiments, we noticed that cells overexpressing MK‐STYX developed more neurites, which often branched. Here, we report that microtubules and microfilaments, components of the cytoskeleton that are involved in the formation of neurites, are present in MK‐STYX‐induced outgrowths. In addition, in response to nerve growth factor (NGF), MK‐STYX‐producing cells produced more actin growth cones than non‐MK‐STYX‐expressing cells. Transmission electron microscopy confirmed that MK‐STYX‐induced neurites form synapses. Furthermore, the expression of Tau‐1 and MAP2 (microtubule associated protein 2) in MK‐STYX‐induced neurites suggests that they have both axonal and dendritic properties. Further studies in hippocampal primary neurons demonstrated that MK‐STYX altered their morphology. A significant number of primary neurons expressing MK‐STYX had more than the normal number of primary neurites. Taken together these data provide evidence that MK‐STYX causes cytoskeletal rearrangement. It also highlights that this unique member of the MKP subfamily has the potential to have a major role in neuronal signaling.Support or Funding InformationThis work was supported by the National Science Foundation Grant MCB1113167 to S.D.H.; Coco Award to S.D.H.; Howard Hughes Medical Research Institute grant through the Undergraduate Science Education Program to the College of William and Mary; a DuPont Fund Student‐Faculty Research Team Stipend awarded to A.D. and S.D.H. through a grant by the Jessie Ball Grant Fund to the William and Mary Scholars for Undergraduate Research Experience program; Ferguson Awards to D.A.B., A.D., and C.S., and the Dintersmith Honors Fellowship to A.D.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.