Phosphorylation in the C-terminal domain of Aquaporin-4 is required for Golgi transition in primary cultured astrocytes

• Published in: Biochemical and biophysical research communications Vol. 377; no. 2; pp. 463 - 468
• Main Authors: Kadohira, Ikuko, Abe, Yoichiro, Nuriya, Mutsuo, Sano, Kazumi, Tsuji, Shoji, Arimitsu, Takeshi, Yoshimura, Yasunori, Yasui, Masato
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 12.12.2008
• Subjects: 60 APPLIED LIFE SCIENCES; Amino Acid Sequence; Amino Acid Substitution; Animals; ANTIBODIES; Aquaporin 4 - genetics; Aquaporin 4 - metabolism; Aquaporin-4 (AQP4); Astrocytes; Astrocytes - metabolism; Astrocytes - ultrastructure; BRAIN; Casein Kinase II - metabolism; GENES; Golgi Apparatus - metabolism; GOLGI COMPLEXES; HOMEOSTASIS; Humans; MICE; MICROSCOPY; MUTANTS; PHOSPHORIC ACID; PHOSPHORUS 32; PHOSPHORYLATION; Protein kinase CK2; Protein Structure, Tertiary; Protein Transport; PROTEINS; Aquaporin-4 (AQP4); Phosphorylation; Protein kinase CK2; Astrocytes
• ISSN: 0006-291X; 1090-2104; 1090-2104
• DOI: 10.1016/j.bbrc.2008.09.155

Aquaporin-4 (AQP4) is expressed in the perivascular and subpial astrocytes end-feet in mammalian brain, and plays a critical component of an integrated water and potassium homeostasis. Here we examine whether AQP4 is phosphorylated in primary cultured mouse astrocytes. Astrocytes were metabolically labeled with [32P]phosphoric acid, then AQP4 was immunoprecipitated with anti-AQP4 antibody. We observed that AQP4 was constitutively phosphorylated, which is reduced by treatment with protein kinase CK2 inhibitors. To elucidate the phosphorylation of AQP4 by CK2, myc-tagged wild-type or mutant AQP4 was transiently transfected in primary cultured astrocytes. Substitution of Ala residues for four putative CK2 phosphorylation sites in the C terminus abolished the phosphorylation of AQP4. Immunofluorescent microscopy revealed that the quadruple mutant was localized in the Golgi apparatus. These observations indicate that the C-terminal domain of AQP4 is constitutively phosphorylated at least in part by protein kinase CK2 and it is required for Golgi transition.