SPAK and OSR1 kinases bind and phosphorylate the β₂-Adrenergic receptor

SPAK and OSR1 are two cytoplasmic serine/threonine protein kinases that regulate the function of a series of sodium, potassium and chloride co-transporters via phosphorylation. Over recent years, it has emerged that these two kinases may have diverse function beyond the regulation of ion co-transporters. Inspired by this, we explored whether SPAK and OSR1 kinases impact physically and phosphorylate the β₂-adrenergic receptor (β₂ADR). Herein, we report that the amino acid sequence of the human β₂ADR displays a SPAK/OSR1 consensus binding motif and using a series of pulldown and in vitro kinase assays we show that SPAK and OSR1 bind the β₂ADR and phosphorylate it in vitro. This work provides a notable example of SPAK and OSR1 kinases binding to a G-protein coupled receptor and taps into the potential of these protein kinases in regulating membrane receptors beyond ion co-transporters.