title: Identification of a new chondropsin class of antitumor compound that selectively inhibits V-ATPases.
abstract: We identify a new naturally occurring class of inhibitor of vacuolar H+-ATPases (V-ATPases) isolated from vacuolar membranes of Neurospora crassa and from chromaffin granule membranes of Bos taurus. To date, the new class includes six chondropsins and poecillastrin A, large polyketide-derived macrolide lactams with 33-37 membered rings. In the National Cancer Institute's 60-cell screen the chondropsin class showed a tumor cell growth inhibitory fingerprint essentially indistinguishable from that of the bafilomycin/concanamycin and the salicylihalamide/lobatamide classes of well-established V-ATPase inhibitors. Half-maximal inhibition of V-ATPase activity in vitro occurred at 0.04-0.7 microM for the fungal vacuolar V-ATPase and at 0.4 to >10 microM for the chromaffin granule V-ATPase. Thus, the new inhibitors are somewhat less potent than the other two classes, which typically have Ki values of <10 nM for V-ATPases, and the new inhibitors differ from the other two classes in their specificity. The bafilomycin class inhibits all eucaryotic V-ATPases, the salicylihalamide class inhibits mammalian V-ATPases but not fungal V-ATPases, and the new chondropsin class inhibits the N. crassa V-ATPase better than the chromaffin granule V-ATPase. Two mutations in the N. crassa V-ATPase that affect the binding of bafilomycin had small but reproducible effects on the affinity of chondropsins for the V-ATPase, suggesting the possibility of a similar mechanism of inhibition.
authors.affiliation: Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, California 95064, USA. rbowman@biology.ucsc.edu
authors.forename: Emma Jean
authors.initials: EJ
authors.lastname: Bowman
authors.forename: Kirk R
authors.initials: KR
authors.lastname: Gustafson
authors.forename: Barry J
authors.initials: BJ
authors.lastname: Bowman
authors.forename: Michael R
authors.initials: MR
authors.lastname: Boyd
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000302:isolation & purification* / Q000494:pharmacology; D002417:Cattle; D002837:Chromaffin Granules / Q000201:enzymology / Q000648:ultrastructure; D004351:Drug Resistance / Q000235:genetics; D004354:Drug Screening Assays, Antitumor; D004791:Enzyme Inhibitors / Q000302:isolation & purification* / Q000494:pharmacology; D007769:Lactams / Q000302:isolation & purification / Q000494:pharmacology; D018942:Macrolides / Q000302:isolation & purification* / Q000494:pharmacology; D009154:Mutation; D009316:National Institutes of Health (U.S.); D009492:Neurospora crassa / Q000201:enzymology / Q000648:ultrastructure; D011161:Porifera / Q000737:chemistry*; D014407:Tumor Cells, Cultured; D014481:United States; D025262:Vacuolar Proton-Translocating ATPases / Q000037:antagonists & inhibitors* / Q000235:genetics
chemical_list: D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; D007769:Lactams; D018942:Macrolides; C440684:chondropsin A; C440685:chondropsin B; C480038:chondropsin C; C440683:chondropsin D; C467924:poecillastrin A; C036978:concanamycin A; C040929:bafilomycin A1; D025262:Vacuolar Proton-Translocating ATPases