Mass spectrometry-based analysis of LRBA phosphorylation

Vasopressin/cAMP/protein kinase A (PKA) signaling phosphorylates AQP2 water channels in renal collecting ducts to reabsorb water from urine for the prevention of further water loss. Lipopolysaccharide-responsive and beige-like anchor protein (LRBA) mediates vasopressin-induced AQP2 phosphorylation; therefore LRBA is essential for urinary concentration. LRBA is identified as the PKA substrates in a mouse cortical collecting duct principal cell line (mpkCCDcl4) whose phosphorylation levels are nearly perfectly correlated with those of AQP2. Although mouse LRBA contains several consensus PKA phosphorylation sites, their phosphorylation status in response to vasopressin remain unknown. Post-translational modification analysis revealed that RRDS1607 and RRIS2189 were phosphorylated by vasopressin.