title: Identification of a phospholemman-like protein from shark rectal glands. Evidence for indirect regulation of Na,K-ATPase by protein kinase c via a novel member of the FXYDY family.
abstract: The Na,K-ATPase provides the driving force for many ion transport processes through control of Na(+) and K(+) concentration gradients across the plasma membranes of animal cells. It is composed of two subunits, alpha and beta. In many tissues, predominantly in kidney, it is associated with a small ancillary component, the gamma-subunit that plays a modulatory role. A novel 15-kDa protein, sharing considerable homology to the gamma-subunit and to phospholemman (PLM) was identified in purified Na,K-ATPase preparations from rectal glands of the shark Squalus acanthias, but was absent in pig kidney preparations. This PLM-like protein from shark (PLMS) was found to be a substrate for both PKA and PKC. Antibodies to the Na, K-ATPase alpha-subunit coimmunoprecipitated PLMS. Purified PLMS also coimmunoprecipitated with the alpha-subunit of pig kidney Na, K-ATPase, indicating specific association with different alpha-isoforms. Finally, PLMS and the alpha-subunit were expressed in stoichiometric amounts in rectal gland membrane preparations. Incubation of membrane bound Na,K-ATPase with non-solubilizing concentrations of C(12)E(8) resulted in functional dissociation of PLMS from Na,K-ATPase and increased the hydrolytic activity. The same effects were observed after PKC phosphorylation of Na,K-ATPase membrane preparations. Thus, PLMS may function as a modulator of shark Na,K-ATPase in a way resembling the phospholamban regulation of the Ca-ATPase.
authors.affiliation: Department of Biophysics and Medical Biochemistry, University of Aarhus, DK-8000 Aarhus C, Denmark.
authors.forename: Y A
authors.initials: YA
authors.lastname: Mahmmoud
authors.forename: H
authors.initials: H
authors.lastname: Vorum
authors.forename: F
authors.initials: F
authors.lastname: Cornelius
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D018118:Chloride Channels; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D004789:Enzyme Activation / Q000187:drug effects; D029941:Fish Proteins; D007700:Kinetics; D008565:Membrane Proteins / Q000737:chemistry* / Q000302:isolation & purification* / Q000378:metabolism; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000737:chemistry* / Q000302:isolation & purification* / Q000378:metabolism; D010766:Phosphorylation; D011092:Polyethylene Glycols / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011233:Precipitin Tests; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism*; D021122:Protein Subunits; D012491:Salt Gland / Q000737:chemistry* / Q000201:enzymology; D017386:Sequence Homology, Amino Acid; D012754:Sharks; D012964:Sodium / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000737:chemistry / Q000378:metabolism*; D012995:Solubility; D013816:Thermodynamics
chemical_list: D018118:Chloride Channels; D029941:Fish Proteins; D008565:Membrane Proteins; C417182:PLMS protein, Squalus acanthias; D010750:Phosphoproteins; D021122:Protein Subunits; C069141:phospholemman; C061442:dodecylnonaoxyethylene glycol monoether; D011092:Polyethylene Glycols; D000255:Adenosine Triphosphate; D012964:Sodium; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium