Aquaporin 0-calmodulin interaction and the effect of aquaporin 0 phosphorylation.
Aquaporin 0 (AQP0), also known as major intrinsic protein of lens, is the most abundant membrane protein in the lens and it undergoes a host of C-terminally directed posttranslational modifications. The C-terminal region containing the major phosphorylation sites is a putative calmodulin-binding site, and calmodulin has been shown to regulate AQP0 water permeability. The purpose of the present study was to elucidate the role of AQP0 phosphorylation on calmodulin binding. AQP0 C-terminal peptides were synthesized with and without serine phosphorylation on S231 and S235, and the ability of these peptides to bind dansyl-labeled calmodulin and the calcium dependence of the interaction was assessed using a fluorescence binding assay. The AQP0 C-terminal phosphorylated peptides were found to have 20-50-fold lower affinities for calmodulin than the unphosphorylated peptide. Chemical cross-linking studies revealed specific sites of AQP0-calmodulin interaction that are significantly reduced by AQP0 phosphorylation. These data suggest that AQP0 C-terminal phosphorylation affects calmodulin binding in vivo and has a role in regulation of AQP0 function.
Rose
K M Lindsey
KM
Department of Cell and Molecular Pharmacology, 173 Ashley Avenue, Medical University of South Carolina, Charleston, South Carolina 29425, USA.
Wang
Z
Z
Magrath
G N
GN
Hazard
E S
ES
Hildebrandt
J D
JD
Schey
K L
KL
D000595:Amino Acid Sequence; D020346:Aquaporins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002147:Calmodulin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D005136:Eye Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D013050:Spectrometry, Fluorescence; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014357:Trypsin / Q000378:metabolism
D020346:Aquaporins; D002147:Calmodulin; D005136:Eye Proteins; D008562:Membrane Glycoproteins; C030328:aquaporin 0; D014357:Trypsin