SCaMC-1Like a member of the mitochondrial carrier (MC) family preferentially expressed in testis and localized in mitochondria and chromatoid body.
Mitochondrial carriers (MC) form a highly conserved family involved in solute transport across the inner mitochondrial membrane in eukaryotes. In mammals, ATP-Mg/Pi carriers, SCaMCs, form the most complex subgroup with four paralogs, SCaMC-1, -2, -3 and -3L, and several splicing variants. Here, we report the tissue distribution and subcellular localization of a mammalian-specific SCaMC paralog, 4930443G12Rik/SCaMC-1Like (SCaMC-1L), which displays unanticipated new features. SCaMC-1L proteins show higher amino acid substitution rates than its closest paralog SCaMC-1. In mouse, SCaMC-1L expression is restricted to male germ cells and regulated during spermatogenesis but unexpectedly its localization is not limited to mitochondrial structures. In mature spermatids SCaMC-1L is detected in the mitochondrial sheath but in previous differentiation stages appears associated to cytosolic granules which colocalize with specific markers of the chromatoid body (CB) in post-meiotic round spermatids and inter-mitochondrial cement (IMC) in spermatocytes. The origin of this atypical distribution was further investigated by transient expression in cell lines. Similarly to male germ cells, in addition to mitochondrial and cytosolic distribution, a fraction of SCaMC-1L-expressing COS-7 cells display cytosolic SCaMC-1L-aggregates which exhibit aggresomal-like features as the CB. Our results indicate that different regions of SCaMC-1L hinder its import into mitochondria and this apparently favours the formation of cytosolic aggregates in COS-7 cells. This mechanism could be also operational in male germ cells and explain the incorporation of SCaMC-1L into germinal granules.
Departamento de Biología Molecular, Centro de Biología Molecular Severo Ochoa UAM-CSIC, and CIBER de Enfermedades Raras (CIBERER), Universidad Autónoma de Madrid, Madrid, Spain.
Ignacio
I
Amigo
Javier
J
Traba
Jorgina
J
Satrústegui
Araceli
A
del Arco
D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism*; D002522:Chlorocebus aethiops; D020440:Gene Duplication; D015870:Gene Expression; D057927:Hydrophobic and Hydrophilic Interactions; D002479:Inclusion Bodies / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D022101:Microtubule-Organizing Center / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D058977:Molecular Sequence Annotation; D008969:Molecular Sequence Data; D009928:Organ Specificity; D058974:Phylogeography; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D012671:Seminiferous Tubules / Q000166:cytology / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013087:Spermatids / Q000378:metabolism; D013737:Testis / Q000166:cytology / Q000378:metabolism
D002135:Calcium-Binding Proteins; D033681:Mitochondrial Membrane Transport Proteins; C579318:SCaMC-1like protein, mouse