Structural Elements in the Transmembrane and Cytoplasmic Domains of the Metal Transporter SLC30A10 Are Required for Its Manganese Efflux Activity

Abstract

Homozygous mutations in SLC30A10 lead to the development of familial manganese-induced parkinsonism. We previously demonstrated that SLC30A10 is a cell surface-localized manganese efflux transporter, and parkinsonism-causing mutations block its trafficking and efflux activity. Interestingly, other transporters in the SLC30 family mediate zinc efflux. Determining the mechanisms that allow SLC30A10 to transport manganese, which are unclear, is essential to understand its role in parkinsonism. Here, we generated a predicted structure of SLC30A10, based on the structure of the bacterial zinc transporter YiiP, and performed functional studies. In YiiP, side chains of residues Asp-45 and Asp-49 in the second and His-153 and Asp-157 in the fifth transmembrane segments coordinate zinc and are required for transport. In SLC30A10, the corresponding residues are Asn-43 and Asp-47 in the second and His-244 and Asp-248 in the fifth transmembrane segments. Surprisingly, although alanine substitution of Asp-248 abolished manganese efflux, that of Asn-43 and Asp-47 did not. Instead, side chains of charged or polar residues adjacent to Asp-248 in the first (Glu-25) or fourth (Asn-127) transmembrane segments were required. Further analyses revealed that residues His-333 and His-350 in the cytoplasmic C-terminal domain were required for full activity. However, the C-terminal domain failed to transfer manganese transport capability to a related zinc transporter. Overall, our results indicate that residues in the transmembrane and C-terminal domains together confer optimal manganese transport capability to SLC30A10 and suggest that the mechanism of ion coordination in the transmembrane domain of SLC30A10 may be substantially different from that in YiiP/other SLC30 proteins.

Manganese metabolism in humans

“…Interestingly, although SLC30A10 mediated Mn efflux, SLC30A1-8 transport Zn. Molecular characterizations as well as crystal structures revealed fundamental differences between a crucial Zn binding site in the transmembrane domain and the corresponding putative metal binding site of SLC30A10 (139) (140,141). Residues in the transmembrane and C-terminal domains together confer optimal manganese transport capability to SLC30A10 (141).…”

“…Molecular characterizations as well as crystal structures revealed fundamental differences between a crucial Zn binding site in the transmembrane domain and the corresponding putative metal binding site of SLC30A10 (139) (140,141). Residues in the transmembrane and C-terminal domains together confer optimal manganese transport capability to SLC30A10 (141). SLC30A10 is localized to the plasma membrane and is functional in manganese metabolism by effluxing cytosolic Mn (142,143).…”

SLC30A10 transporter in the digestive system regulates brain manganese under basal conditions while brain SLC30A10 protects against neurotoxicity

“…We recently described generation of homozygous floxed Slc30a10 mice (Slc30a10 fl/fl ) in which exon 1 of Slc30a10 was flanked by loxP sites (22). Exon 1 codes for amino acids 1-205 of mouse SLC30A10, which encompass most of the transmembrane domain required for manganese transport (21,22). To briefly summarize here, the targeting vector was electroporated into V6.5 embryonic stem cells (C57BL/ 6 ϫ 129S4/SvJae) (22).…”

Influence of iron metabolism on manganese transport and toxicity

“…SLC30A10 is localized the cell surface as well as intracellular compartments of secretory pathways 103 . Both transmembrane and C-terminal domains of cell membrane-associated SLC30A10 are structurally critical for Mn export activity 112 . Mutated SLC30A10 is unable to traffic to the cell surface and thereby decreases Mn efflux activity 110 .…”