cAMP‐dependent protein kinase activation affects vasopressin V2‐receptor number and internalization in LLC‐PK1 renal epithelial cells

Abstract

The relationship between activation of the cAMP‐dependent protein kinase (cAMP‐PK) and ligand binding and internalization by the vasopressin renal (V₂‐type) receptor of LLC‐PK₁ renal epithelial cells was examined. Upon cAMP‐PK activation through 1 h treatment with the cAMP analogue 8‐bromo‐cAMP (BrcA), a marked reduction in V₂‐receptor steady state number and internalization in LLC‐PK₁ cells was effected. In cells treated for 17 h with BrcA and hence down‐regulated for cAMP‐PK₁ the V₂‐receptor number was normal but internalization was markedly reduced. Cells of the LLC‐PK₁ mutant FIB4, which possesses about 10% parental cAMP‐PK catalytic subunit activity, exhibited lower V₂‐receptor steady state number and internalization in comparison to untreated LLC‐PK₁ cells. A negative correlation was thus evident between cAMP‐PK activation and V₂‐receptor number and internalization. Phosphorylation by cAMP‐PK may effect ligand‐independent removal of receptor from the plasma membrane.