Novel regulation of aquaporins during osmotic stress.
Aquaporin protein regulation and redistribution in response to osmotic stress was investigated. Ice plant (Mesembryanthemum crystallinum) McTIP1;2 (McMIPF) mediated water flux when expressed in Xenopus leavis oocytes. Mannitol-induced water imbalance resulted in increased protein amounts in tonoplast fractions and a shift in protein distribution to other membrane fractions, suggesting aquaporin relocalization. Indirect immunofluorescence labeling also supports a change in membrane distribution for McTIP1;2 and the appearance of a unique compartment where McTIP1;2 is expressed. Mannitol-induced redistribution of McTIP1;2 was arrested by pretreatment with brefeldin A, wortmannin, and cytochalasin D, inhibitors of vesicle trafficking-related processes. Evidence suggests a role for glycosylation and involvement of a cAMP-dependent signaling pathway in McTIP1;2 redistribution. McTIP1;2 redistribution to endosomal compartments may be part of a homeostatic process to restore and maintain cellular osmolarity under osmotic-stress conditions.
Vera-Estrella
Rosario
R
Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de Mexico, Cuernavaca, Morelos 62250, Mexico. rosario@ibt.unam.mx
Barkla
Bronwyn J
BJ
Bohnert
Hans J
HJ
Pantoja
Omar
O
D020346:Aquaporins / Q000502:physiology*; D018744:DNA, Plant / Q000235:genetics; D006031:Glycosylation; D035723:Mesembryanthemum / Q000502:physiology*; D009994:Osmolar Concentration; D018515:Plant Leaves / Q000502:physiology; D010940:Plant Proteins / Q000378:metabolism / Q000502:physiology*; D018517:Plant Roots / Q000502:physiology; D012315:RNA Caps / Q000235:genetics; D018749:RNA, Plant / Q000235:genetics; D014158:Transcription, Genetic
D020346:Aquaporins; D018744:DNA, Plant; D010940:Plant Proteins; D012315:RNA Caps; D018749:RNA, Plant