title: Modulation of P-glycoprotein ATPase of Helicoverpa armigera by cholesterol: effects on ATPase activity and interaction of insecticides.
abstract: Purified P-glycoprotein ATPase from Helicoverpa armigera (Ha-Pgp), reconstituted in proteoliposomes composed of phospholipids and cholesterol, shows higher ATPase activity in the presence of cholesterol than in its absence. The Ha-Pgp ATPase activity was increased 30-40% with cholesterol. The KM for ATP was found to be 1 and 0.8 mM in the absence and presence of cholesterol, respectively. The insecticide-stimulated Ha-Pgp ATPase activity was increased by 10-20% for all the insecticides in the reconstituted proteoliposomes containing cholesterol compared to those with no cholesterol. The effects of cholesterol on KM and Vmax values of insecticide-stimulated Ha-Pgp ATPase activity were unrelated to the size of the insecticide. Ha-Pgp tryptophan fluorescence displayed a red shift of 3 and 8 nm in emission spectra upon binding of insecticides. Cholesterol enhances the interaction of insecticides with Ha-Pgp. Kd values of different insecticides for binding to Ha-Pgp were found to be lower in the presence of cholesterol in the proteoliposomes compared to its absence. Results suggest that cholesterol plays a role in the recognition and interaction of insecticides by modulating Ha-Pgp ATPase and may be involved in efflux of insecticides from cells by the transporter.
authors.affiliation: Department of Biochemistry, Gulbarga University, Gulbarga, Karnataka, India.
authors.forename: Ravindra M
authors.initials: RM
authors.lastname: Aurade
authors.forename: Senigala K
authors.initials: SK
authors.lastname: Jayalakshmi
authors.forename: Shashikant S
authors.initials: SS
authors.lastname: Udikeri
authors.forename: Kuruba
authors.initials: K
authors.lastname: Sreeramulu
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D002784:Cholesterol / Q000008:administration & dosage / Q000378:metabolism*; D007306:Insecticides / Q000494:pharmacology*; D009036:Moths / Q000187:drug effects* / Q000378:metabolism*; D011510:Proteolipids / Q000378:metabolism
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D007306:Insecticides; D011510:Proteolipids; C020485:proteoliposomes; D002784:Cholesterol; D000251:Adenosine Triphosphatases