OXSR1 is a serine/threonine kinase which regulates downstream kinases in response to environmental stress such as osmotic stresses, notably sorbitol and, to a lesser extent, NaCl. OXSR1 phosphorylated thr84 within the N-terminal regulatory domain of PAK1. Replacement of thr84 with gln reduced activation of PAK1 by an active form of the small G protein CDC42, suggesting that phosphorylation by OXSR1 modulates the G protein sensitivity of PAK. OXSR1 interacts with chloride channel proteins SLC12A6 isoform 2, SLC12A1 and SLC12A2 but not with SLC12A4 and SLC12A7, possibly establishing sensor/signaling modules that initiate the cellular response to environmental stress. Binds to and phosphorylates RELL1, RELL2 AND RELT. OXSR1 may have a role in regulating the actin cytoskeleton.