title: Carbonic anhydrases IV and IX: subcellular localization and functional role in mouse skeletal muscle.
abstract: The subcellular localization of carbonic anhydrase (CA) IV and CA IX in mouse skeletal muscle fibers has been studied immunohistochemically by confocal laser scanning microscopy. CA IV has been found to be located on the plasma membrane as well as on the sarcoplasmic reticulum (SR) membrane. CA IX is not localized in the plasma membrane but in the region of the t-tubular (TT)/terminal SR membrane. CA IV contributes 20% and CA IX 60% to the total CA activity of SR membrane vesicles isolated from mouse skeletal muscles. Our aim was to examine whether SR CA IV and TT/SR CA IX affect muscle contraction. Isolated fiber bundles of fast-twitch extensor digitorum longus and slow-twitch soleus muscle from mouse were investigated for isometric twitch and tetanic contractions and by a fatigue test. The muscle functions of CA IV knockout (KO) fibers and of CA IX KO fibers do not differ from the function of wild-type (WT) fibers. Muscle function of CA IV/XIV double KO mice unexpectedly shows a decrease in rise and relaxation time and in force of single twitches. In contrast, the CA inhibitor dorzolamide, whether applied to WT or to double KO muscle fibers, leads to a significant increase in rise time and force of twitches. It is concluded that the function of mouse skeletal muscle fibers expressing three membrane-associated CAs, IV, IX, and XIV, is not affected by the lack of one isoform but is possibly affected by the lack of all three CAs, as indicated by the inhibition studies.
authors.affiliation: Zentrum Biochemie, Medizinische Hochschule Hannover, Carl-Neuberg-Str. 1, 30625 Hannover, Germany.
authors.forename: Renate J
authors.initials: RJ
authors.lastname: Scheibe
authors.forename: Karsten
authors.initials: K
authors.lastname: Mundhenk
authors.forename: Tilman
authors.initials: T
authors.lastname: Becker
authors.forename: Janine
authors.initials: J
authors.lastname: Hallerdei
authors.forename: Abdul
authors.initials: A
authors.lastname: Waheed
authors.forename: Gul N
authors.initials: GN
authors.lastname: Shah
authors.forename: William S
authors.initials: WS
authors.lastname: Sly
authors.forename: Gerolf
authors.initials: G
authors.lastname: Gros
authors.forename: Petra
authors.initials: P
authors.lastname: Wetzel
mesh_terms: D000818:Animals; D030741:Carbonic Anhydrase IV / Q000235:genetics / Q000378:metabolism*; D000071231:Carbonic Anhydrase IX; D002256:Carbonic Anhydrases / Q000235:genetics / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics; D007150:Immunohistochemistry; D051379:Mice; D018345:Mice, Knockout; D018613:Microscopy, Confocal; D009119:Muscle Contraction / Q000235:genetics; D018656:Muscle Fibers, Fast-Twitch / Q000201:enzymology / Q000648:ultrastructure; D018657:Muscle Fibers, Slow-Twitch / Q000201:enzymology / Q000648:ultrastructure; D018482:Muscle, Skeletal / Q000201:enzymology* / Q000648:ultrastructure; D012508:Sarcolemma / Q000201:enzymology / Q000648:ultrastructure; D012519:Sarcoplasmic Reticulum / Q000201:enzymology / Q000648:ultrastructure; D013449:Sulfonamides / Q000494:pharmacology; D013876:Thiophenes / Q000494:pharmacology; D013997:Time Factors; D022161:Transport Vesicles / Q000201:enzymology / Q000648:ultrastructure
chemical_list: D004791:Enzyme Inhibitors; D013449:Sulfonamides; D013876:Thiophenes; C062765:dorzolamide; D030741:Carbonic Anhydrase IV; D000071231:Carbonic Anhydrase IX; D002256:Carbonic Anhydrases; C492796:Car9 protein, mouse