Ser-256 phosphorylation dynamics of Aquaporin 2 during maturation from the ER to the vesicular compartment in renal cells

Aquaporin 2 (AQP2) phosphorylation at Ser-256 by protein kinase A (PKA) is a key signal for vasopressin-stimulated AQP2 insertion into the plasma membrane in renal cells. This study underscores the possible role of phosphorylation at Ser-256 in regulating AQP2 maturation. AQP2-transfected renal CD8...

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Published inThe FASEB journal Vol. 17; no. 13; p. 1886
Main Authors Procino, Giuseppe, Carmosino, Monica, Marin, Oriano, Brunati, Anna M, Contri, Antonella, Pinna, Lorenzo A, Mannucci, Roberta, Nielsen, Soren, Kwon, Tae-Hwan, Svelto, Maria, Valenti, Giovanna
Format Journal Article
LanguageEnglish
Published United States 01.10.2003
Subjects
Aquaporin 2
Aquaporin 6
Aquaporins - chemistry
Aquaporins - genetics
Aquaporins - metabolism
Cell Line
Consensus Sequence
Diabetes Insipidus, Nephrogenic - genetics
Endoplasmic Reticulum - metabolism
Golgi Apparatus - metabolism
Humans
Kidney - metabolism
Lysosomes - metabolism
Models, Biological
Mutation
Phosphorylation
Protein Transport
Protein-Serine-Threonine Kinases - metabolism
Serine - metabolism
Transport Vesicles - metabolism
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Summary:Aquaporin 2 (AQP2) phosphorylation at Ser-256 by protein kinase A (PKA) is a key signal for vasopressin-stimulated AQP2 insertion into the plasma membrane in renal cells. This study underscores the possible role of phosphorylation at Ser-256 in regulating AQP2 maturation. AQP2-transfected renal CD8 cells were incubated with brefeldin A (BFA) to accumulate newly synthesized AQP2 in the endoplasmic reticulum (ER), and AQP2 flow from ER to the vesicular compartment was analyzed after BFA washout. We found that a) in the ER, AQP2 is weakly phosphorylated; b) the amount of phosphorylated AQP2 (p-AQP2) at Ser-256 increased significantly during transit in the Golgi, even in the presence of the PKA inhibitor H89; and c) AQP2 transport from the Golgi to the vasopressin-regulated vesicular compartment occurred with a concomitant decrease in p-AQP2 at Ser-256. These results support the hypothesis that AQP2 transition in the Golgi apparatus is associated with a PKA-independent increase in AQP2 phosphorylation at Ser-256. Conversely, impaired constitutive phosphorylation in a Golgi-associated compartment occurring in cells expressing mutated S256A-AQP2 or E258K-AQP2 causes phosphorylation-defective AQP2 routing to lysosomes. This result might explain the molecular basis of the dominant form of nephrogenic diabetes insipidus caused by the mutation E258K-AQP2, in which the phenotype is caused by an impaired routing of AQP2.
ISSN:1530-6860