title: Ultrastructural localization of aquaporin 4 and alpha1-syntrophin in the vascular feet of brain astrocytes.
abstract: Aquaporin 4 (AQP4) is a recently discovered membrane bound water-selective channel and has been described at the light microscopic level to be predominantly expressed in the astrocytes of the brain, especially at the perivascular astrocyte endfoot processes. Alpha1-syntrophin, a member of dystrophin-associated protein, has also been reported at the light microscopic to be expressed level in the same site of astrocytes as AQP4 and interacts with other molecules through its PDZ domain. AQP4 expression has been reported to be absent at the sarcolemma and the perivascular astrocyte endfoot processes of alpha1-syntrophin knockout mice. Based on these observations, the molecular association between AQP4 and alpha1-syntrophin could be speculated. To test this hypothesis, we investigated the ultrasturctural localization of AQP4 and alpha1-syntrophin in the brain astrocytes by using double immunogold labeled electron microscopy. The results showed that AQP4 and alpha1-syntrophin colocalized frequently at the astrocyte membrane, especially at the perivascular astrocyte endfoot processes and suggested the presence of linkage between AQP4 and alpha1-syntrophin at the astrocyte plasma membrane.
authors.affiliation: Department of Neurology, Showa University Fujigaoka Hospital, Yokohama, Japan. inoue834@dc.mbn.or.jp
authors.forename: Masahiko
authors.initials: M
authors.lastname: Inoue
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Wakayama
authors.forename: Jian Wu
authors.initials: JW
authors.lastname: Liu
authors.forename: Makoto
authors.initials: M
authors.lastname: Murahashi
authors.forename: Seiji
authors.initials: S
authors.lastname: Shibuya
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Oniki
mesh_terms: D000818:Animals; D051401:Aquaporin 4; D020346:Aquaporins / Q000378:metabolism*; D001253:Astrocytes / Q000378:metabolism* / Q000648:ultrastructure*; D001921:Brain / Q000166:cytology / Q000378:metabolism*; D002135:Calcium-Binding Proteins; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D015151:Immunoblotting; D007150:Immunohistochemistry; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008854:Microscopy, Electron; D009124:Muscle Proteins / Q000378:metabolism*; D014018:Tissue Distribution
chemical_list: C496031:Aqp4 protein, mouse; D051401:Aquaporin 4; D020346:Aquaporins; D002135:Calcium-Binding Proteins; D008565:Membrane Proteins; D009124:Muscle Proteins; C091825:syntrophin alpha1