title: The sarcolemmal calcium pump, alpha-1 syntrophin, and neuronal nitric-oxide synthase are parts of a macromolecular protein complex.
abstract: The main role of the plasma membrane Ca2+/calmodulin-dependent ATPase (PMCA) is in the removal of Ca2+ from the cytosol. Recently, we and others have suggested a new function for PMCA as a modulator of signal transduction pathways. This paper shows the physical interaction between PMCA (isoforms 1 and 4) and alpha-1 syntrophin and proposes a ternary complex of interaction between endogenous PMCA, alpha-1 syntrophin, and NOS-1 in cardiac cells. We have identified that the linker region between the pleckstrin homology 2 (PH2) and the syntrophin unique (SU) domains, corresponding to amino acids 399-447 of alpha-1 syntrophin, is crucial for interaction with PMCA1 and -4. The PH2 and the SU domains alone failed to interact with PMCA. The functionality of the interaction was demonstrated by investigating the inhibition of neuronal nitric-oxide synthase-1 (NOS-1); PMCA is a negative regulator of NOS-1-dependent NO production, and overexpression of alpha-1 syntrophin and PMCA4 resulted in strongly increased inhibition of NO production. Analysis of the expression levels of alpha-1 syntrophin protein in the heart, skeletal muscle, brain, uterus, kidney, or liver of PMCA4-/- mice, did not reveal any differences when compared with those found in the same tissues of wild-type mice. These results suggest that PMCA4 is tethered to the syntrophin complex as a regulator of NOS-1, but its absence does not cause collapse of the complex, contrary to what has been reported for other proteins within the complex, such as dystrophin. In conclusion, the present data demonstrate for the first time the localization of PMCA1b and -4b to the syntrophin.dystrophin complex in the heart and provide a specific molecular mechanism of interaction as well as functionality.
authors.affiliation: Division of Cardiology, Room 1.302 Stopford Building, The University of Manchester, Oxford Road, Manchester, M13 9PT, United Kingdom.
authors.forename: Judith C
authors.initials: JC
authors.lastname: Williams
authors.forename: Angel L
authors.initials: AL
authors.lastname: Armesilla
authors.forename: Tamer M A
authors.initials: TM
authors.lastname: Mohamed
authors.forename: Cassandra L
authors.initials: CL
authors.lastname: Hagarty
authors.forename: Fiona H
authors.initials: FH
authors.lastname: McIntyre
authors.forename: Sybille
authors.initials: S
authors.lastname: Schomburg
authors.forename: Aly O
authors.initials: AO
authors.lastname: Zaki
authors.forename: Delvac
authors.initials: D
authors.lastname: Oceandy
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Cartwright
authors.forename: Mamta H
authors.initials: MH
authors.lastname: Buch
authors.forename: Michael
authors.initials: M
authors.lastname: Emerson
authors.forename: Ludwig
authors.initials: L
authors.lastname: Neyses
mesh_terms: D000818:Animals; D002135:Calcium-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000737:chemistry* / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D027682:Cation Transport Proteins / Q000737:chemistry* / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D016189:Dystrophin / Q000502:physiology; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D009124:Muscle Proteins / Q000737:chemistry* / Q000378:metabolism; D018482:Muscle, Skeletal / Q000201:enzymology* / Q000378:metabolism; D009206:Myocardium / Q000737:chemistry* / Q000201:enzymology / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I / Q000737:chemistry* / Q000378:metabolism; D053499:Plasma Membrane Calcium-Transporting ATPases; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012508:Sarcolemma / Q000201:enzymology* / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology
chemical_list: C506952:ATP2B1 protein, human; D002135:Calcium-Binding Proteins; D027682:Cation Transport Proteins; D016189:Dystrophin; D008565:Membrane Proteins; D009124:Muscle Proteins; C091825:syntrophin alpha1; D052248:Nitric Oxide Synthase Type I; C507517:ATP2B4 protein, human; D053499:Plasma Membrane Calcium-Transporting ATPases; C506954:Atp2b1 protein, mouse; D000252:Calcium-Transporting ATPases