title: Carbonic anhydrase XIV identified as the membrane CA in mouse retina: strong expression in Müller cells and the RPE.
abstract: The presence of carbonic anhydrase (CA) activity in the neural retina has been known for several decades. CA-II, a soluble cytoplasmic isoform expressed by Müller cells and a subset of amacrine cells, was thought to be the sole source of CA activity in the neural retina. However, CA-II deficient mice retain CA activity in the neural retina, which implies that another isoform must be present in that tissue. Recently CA-XIV, an integral membrane protein, was cloned and characterized. We, therefore, sought to determine whether CA-XIV is expressed in the neural retina, and hence is responsible for the CA activity observed in CA-II null animals. Immunohistochemical analyses of histological sections from CA-II null, CA-XIV null, and control mice were performed to localize the CA-XIV isoform, as well as other known retinal markers. Immunoblotting and real-time RT-PCR analyses were also performed to test for CA-XIV expression in retina and other mouse tissues. We determined herein that CA-XIV, a approximately 45kDa membrane protein, is expressed in retina, as it is in kidney. In the retina, CA-XIV is expressed on the plasma membrane of Müller cells. CA-XIV is also found on both the apical and basal membranes of the retinal pigmented epithelium. The data presented here indicate that like CA-II, CA-XIV is highly expressed in the neural retina and, like CA-II, more specifically by the Müller cells. The cellular compartmentalization of the two isoforms in the Müller cell-one cytoplasmic and the other on the plasma membrane-suggest that the two enzymes have specific and unique functions. Future studies will be necessary to assign functions to CA-II and CA-XIV in the mouse neural retina.
authors.affiliation: Whitney Laboratory for Marine Bioscience, The University of Florida, 9505 Ocean Shore Blvd, St Augustine, FL 32080, USA.
authors.forename: Judith D
authors.initials: JD
authors.lastname: Ochrietor
authors.forename: Michael F
authors.initials: MF
authors.lastname: Clamp
authors.forename: Tatiana P
authors.initials: TP
authors.lastname: Moroz
authors.forename: Jeffrey H
authors.initials: JH
authors.lastname: Grubb
authors.forename: Gul N
authors.initials: GN
authors.lastname: Shah
authors.forename: Abdul
authors.initials: A
authors.lastname: Waheed
authors.forename: William S
authors.initials: WS
authors.lastname: Sly
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Linser
mesh_terms: D000818:Animals; D024402:Carbonic Anhydrase II / Q000378:metabolism; D002256:Carbonic Anhydrases / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D015151:Immunoblotting; D007527:Isoenzymes / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008856:Microscopy, Fluorescence; D010857:Pigment Epithelium of Eye / Q000201:enzymology; D012333:RNA, Messenger / Q000235:genetics; D012160:Retina / Q000201:enzymology*; D012165:Retinal Ganglion Cells / Q000201:enzymology; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods
chemical_list: D007527:Isoenzymes; D012333:RNA, Messenger; D024402:Carbonic Anhydrase II; D002256:Carbonic Anhydrases; C466621:carbonic anhydrase XIV