title: A galanin-mastoparan chimeric peptide activates the Na+,K(+)-ATPase and reverses its inhibition by ouabain.
abstract: The effect of the neuropeptide galanin, the wasp venom toxin amphiphilic peptide toxin mastoparan and the chimeric peptide, galparan, consisting of N-terminal 13 amino acids of neuropeptide galanin linked at C-terminus to mastoparan amide (and its inactive analog Mas17) on the activity of Na+,K(+)-ATPase has been studied. Mastoparan inhibits the activity of the Na+,K(+)-ATPase with IC50 = 7.5 microM and also reduces the cooperativity for Na+ and K+, respectively, while galanin has no effect on the Na+,K(+)-ATPase activity. The chimeric peptide, galanin(1-13)-mastoparan amide (galparan), exhibits biphasic interaction with Na+,K(+)-ATPase, it activates the enzyme at maximal stimulating concentration of 4 microM followed by inhibition of the enzyme with IC50 of 100 microM. At maximum stimulating concentration (4 microM), galparan partly reduces the cooperativity only for Na+ and it also counteracts the inhibitory effect of oubain on Na+,K(+)-ATPase. Galparan's stimulatory effect was influenced by ATP. The chimeric peptide [19Lys,26Leu]-galparan, containing the inactive analog of mastoparan (Mas17), has no effects on rat brain Na+,K(+)-ATPase activity. Both chimeric peptides galparan and [19Lys,26Leu]-galparan are high-affinity galanin receptor ligands with IC50 of 6.4 nM and 0.71 nM, respectively, while galanin (1-13) and mastoparan alone have significantly lower affinity for the galanin receptor, IC50 of 125 nM and 1 microM, respectively. The ability of chimeric peptides to bind to galanin receptors does not correlate with their effects on the Na+,K(+)-ATPase.
authors: Department of Neurochemistry and Neurotoxicology, Stockholm University, Sweden. ulo@neurochem.su.se
authors: U
authors: U
authors: Langel
authors: M
authors: M
authors: Pooga
authors: C
authors: C
authors: Kairane
authors: M
authors: M
authors: Zilmer
authors: T
authors: T
authors: Bartfai
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000633:toxicity*; D005625:Frontal Lobe / Q000201:enzymology; D019004:Galanin / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D036341:Intercellular Signaling Peptides and Proteins; D007928:Lethal Dose 50; D008969:Molecular Sequence Data; D010042:Ouabain / Q000633:toxicity*; D010455:Peptides; D051381:Rats; D017208:Rats, Wistar; D044088:Receptors, Galanin; D011964:Receptors, Gastrointestinal Hormone / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013552:Swine; D014862:Wasp Venoms / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D004791:Enzyme Inhibitors; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D044088:Receptors, Galanin; D011964:Receptors, Gastrointestinal Hormone; D011993:Recombinant Fusion Proteins; D014862:Wasp Venoms; D010042:Ouabain; C037500:mastoparan; D019004:Galanin; D000254:Sodium-Potassium-Exchanging ATPase