title: Endogenous sterol biosynthesis is important for mitochondrial function and cell morphology in procyclic forms of Trypanosoma brucei.
abstract: Sterol biosynthesis inhibitors are promising entities for the treatment of trypanosomal diseases. Insect forms of Trypanosoma brucei, the causative agent of sleeping sickness, synthesize ergosterol and other 24-alkylated sterols, yet also incorporate cholesterol from the medium. While sterol function has been investigated by pharmacological manipulation of sterol biosynthesis, molecular mechanisms by which endogenous sterols influence cellular processes remain largely unknown in trypanosomes. Here we analyse by RNA interference, the effects of a perturbation of three specific steps of endogenous sterol biosynthesis in order to dissect the role of specific intermediates in proliferation, mitochondrial function and cellular morphology in procyclic cells. A decrease in the levels of squalene synthase and squalene epoxidase resulted in a depletion of cellular sterol intermediates and end products, impaired cell growth and led to aberrant morphologies, DNA fragmentation and a profound modification of mitochondrial structure and function. In contrast, cells deficient in sterol methyl transferase, the enzyme involved in 24-alkylation, exhibited a normal growth phenotype in spite of a complete abolition of the synthesis and content of 24-alkyl sterols. Thus, the data provided indicates that while the depletion of squalene and post-squalene endogenous sterol metabolites results in profound cellular defects, bulk 24-alkyl sterols are not strictly required to support growth in insect forms of T. brucei in vitro.
authors.affiliation: Instituto de Parasitología y Biomedicina López-Neyra, Consejo Superior de Investigaciones Científicas, Avda. del Conocimiento s/n, Armilla, Granada, Spain.
authors.forename: Guiomar
authors.initials: G
authors.lastname: Pérez-Moreno
authors.forename: Marco
authors.initials: M
authors.lastname: Sealey-Cardona
authors.forename: Carlos
authors.initials: C
authors.lastname: Rodrigues-Poveda
authors.forename: Michael H
authors.initials: MH
authors.lastname: Gelb
authors.forename: Luis Miguel
authors.initials: LM
authors.lastname: Ruiz-Pérez
authors.forename: Víctor
authors.initials: V
authors.lastname: Castillo-Acosta
authors.forename: Julio A
authors.initials: JA
authors.lastname: Urbina
authors.forename: Dolores
authors.initials: D
authors.lastname: González-Pacanowska
mesh_terms: D000818:Animals; D000962:Antimalarials / Q000494:pharmacology; D048430:Cell Shape; D053938:DNA Fragmentation; D004318:Doxycycline / Q000494:pharmacology; D013186:Farnesyl-Diphosphate Farnesyltransferase / Q000235:genetics / Q000378:metabolism; D017353:Gene Deletion; D015971:Gene Expression Regulation, Enzymologic; D008928:Mitochondria / Q000378:metabolism*; D034622:RNA Interference / Q000187:drug effects; D050603:Squalene Monooxygenase / Q000235:genetics / Q000378:metabolism; D013261:Sterols / Q000096:biosynthesis*; D014346:Trypanosoma brucei brucei / Q000166:cytology* / Q000502:physiology*
chemical_list: D000962:Antimalarials; D013261:Sterols; D050603:Squalene Monooxygenase; D013186:Farnesyl-Diphosphate Farnesyltransferase; D004318:Doxycycline