Tex264 Binding to SNX27 Regulates Itgα5 Receptor Membrane Recycling and Affects Cell Migration.

Tex264 is an endoplasmic reticulum (ER) membrane protein that was recently demonstrated to act as an ER-phagy receptor under starvation conditions to mediate endoplasmic reticulum autophagy. However, how Tex264 functions in the central nervous system (CNS) and tumors is unclear. Here, we identified 89 proteins from the rat brain that may specifically interact with Tex264 and confirmed the interaction between sorting nexin 27 (SNX27) and Tex264 by coimmunoprecipitation and immunofluorescence. Our results indicated that Tex264 may promote recycling of membrane proteins from endosomes to the cell plasma membrane by recruiting SNX27 retromer vesicles. siRNA-mediated knockdown of TEX264 in HeLa cells did not affect cell proliferation but did significantly inhibit cell migration through a mechanism that may involve a reduction in SNX27-mediated Itgα5 receptor membrane recycling. Results of this study helped identify potential binding Tex264 partners and provide insights into Tex264 functions in the CNS and in tumors.

WNK3-PER1 interactions regulate the circadian rhythm in the suprachiasmatic nucleus in rats.

PER1 is a core component of the internal time-keeping system. In the suprachiasmatic nucleus, it serves as the primary circadian pacemaker in mammalian brains. PER1 functions with other clock components to generate a feedback loop involving the transcriptional repression of gene expression to produce a circadian rhythm with an approximately 24-hour cycle. Post-transcriptional modifications (PTMs) are a basic regulatory mechanism that both perpetuate self-sustained oscillations and interpret metabolic input into circadian physiology by affecting factors such as protein stability, interactions, localization, and activity. Here we examined whether the serine/threonine protein kinase WNK3, which is expressed in a circadian rhythm, can interact and colocalize with PER1 in the SCN. In rats, WNK3 knockdown in the SCN is associated with altered sleep patterns. Moreover, WNK3 can phosphorylate PER1 to promote its degradation and is associated with circadian oscillations when PER1 is expressed in vitro.

Revealing PAK2's Function in the Cell Division through MKLP1's Interactome.

Cell division-related proteins are essential for the normal development and differentiation of cells and may be related to the occurrence of cancer and the drug resistance mechanism of cancer cells. The mitotic kinesin-like protein 1 (MKLP1) is a kinesin protein that has been involved in the assembly of the midzone/midbody during mitosis and cytokinesis. In this study, we found that the tail domain of MKLP1 exhibited an autoinhibitory effect on its motor activity. Overexpression of the tail domain in HEK293 cells blocked cytokinesis and caused bi-/multinucleation. It is possible that protein binding to the MKLP1 tail relieves this autoinhibition and induces the motility of MKLP1. We used the GST pull-down assay followed by the LC-MS/MS analysis and identified 54 MKLP1 tail domain-specific binding proteins. Further, we confirmed the MS result by coimmunoprecipitation and FRET that a serine/threonine kinase, p21-activated kinase 2 (PAK2), binding to MKLP1. Endogenous PAK2 expression was found to be identical to that of MKLP1 in HEK293 cells during cytokinesis. Finally, functional studies indicated that when PAK2 expression was downregulated by siRNA, MKLP1 underwent a change in its localization away from the midbody, and cell cytokinesis was subsequently impeded. This study presents a novel regulatory mechanism that PAK2 promotes the activation of MKLP1 and contributes to complete cell cytokinesis.