title: Human sperm tail proteome suggests new endogenous metabolic pathways.
abstract: Proteomic studies are contributing greatly to our understanding of the sperm cell, and more detailed descriptions are expected to clarify additional cellular and molecular sperm attributes. The aim of this study was to characterize the subcellular proteome of the human sperm tail and, hopefully, identify less concentrated proteins (not found in whole cell proteome studies). Specifically, we were interested in characterizing the sperm metabolic proteome and gaining new insights into the sperm metabolism issue. Sperm were isolated from normozoospermic semen samples and depleted of any contaminating leukocytes. Tail fractions were obtained by means of sonication followed by sucrose-gradient ultracentrifugation, and their purity was confirmed via various techniques. Liquid chromatography and tandem mass spectrometry of isolated sperm tail peptides resulted in the identification of 1049 proteins, more than half of which had not been previously described in human sperm. The categorization of proteins according to their function revealed two main groups: proteins related to metabolism and energy production (26%), and proteins related to sperm tail structure and motility (11%). Interestingly, a great proportion of the metabolic proteome (24%) comprised enzymes involved in lipid metabolism, including enzymes for mitochondrial beta-oxidation. Unexpectedly, we also identified various peroxisomal proteins, some of which are known to be involved in the oxidation of very long chain fatty acids. Analysis of our data using Reactome suggests that both mitochondrial and peroxisomal pathways might indeed be active in sperm, and that the use of fatty acids as fuel might be more preponderant than previously thought. In addition, incubation of sperm with the fatty acid oxidation inhibitor etomoxir resulted in a significant decrease in sperm motility. Contradicting a common concept in the literature, we suggest that the male gamete might have the capacity to obtain energy from endogenous pools, and thus to adapt to putative exogenous fluctuations.
authors.affiliation: Human Genetics Research Group, IDIBAPS, Faculty of Medicine, University of Barcelona, Casanova 143, 08036 Barcelona, Spain.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Amaral
authors.forename: Judit
authors.initials: J
authors.lastname: Castillo
authors.forename: Josep Maria
authors.initials: JM
authors.lastname: Estanyol
authors.forename: José Luís
authors.initials: JL
authors.lastname: Ballescà
authors.forename: João
authors.initials: J
authors.lastname: Ramalho-Santos
authors.forename: Rafael
authors.initials: R
authors.lastname: Oliva
mesh_terms: D002499:Centrifugation, Density Gradient; D002853:Chromatography, Liquid; D055032:Electron Microscope Tomography; D004734:Energy Metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004852:Epoxy Compounds / Q000494:pharmacology; D005227:Fatty Acids / Q000378:metabolism; D006801:Humans; D050356:Lipid Metabolism; D008297:Male; D008928:Mitochondria / Q000737:chemistry / Q000378:metabolism; D010084:Oxidation-Reduction; D020675:Peroxisomes / Q000737:chemistry / Q000378:metabolism; D020543:Proteome / Q000378:metabolism*; D013010:Sonication; D013081:Sperm Motility / Q000502:physiology*; D013082:Sperm Tail / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D053719:Tandem Mass Spectrometry
chemical_list: D004791:Enzyme Inhibitors; D004852:Epoxy Compounds; D005227:Fatty Acids; D020543:Proteome; C054207:etomoxir