Journal
BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS
Volume 377, Issue 2, Pages 463-468Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.bbrc.2008.09.155
Keywords
Aquaporin-4 (AQP4); Phosphorylation; Protein kinase CK2; Astrocytes
Categories
Funding
- Specially Promoted Research
- Global Center of Excellence Program for Humanoid Metabolomic Systems Biology
- Ministry of Education, Culture, Sports, Science and Technology (MEXT).
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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 [(32)p]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. (C) 2008 Elsevier Inc. All rights reserved.
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