Structural prediction of two novel human atypical SLC transporters, MFSD4A and MFSD9, and their neuroanatomical distribution in mice

PLoS One. 2017 Oct 19;12(10):e0186325. doi: 10.1371/journal.pone.0186325. eCollection 2017.

Abstract

Out of the 430 known solute carriers (SLC) in humans, 30% are still orphan transporters regarding structure, distribution or function. Approximately one third of all SLCs belong to the evolutionary conserved and functionally diverse Major Facilitator Superfamily (MFS). Here, we studied the orphan proteins, MFSD4A and MFSD9, which are atypical SLCs of MFS type. Hidden Markov Models were used to identify orthologues in several vertebrates, and human MFSD4A and MFSD9 share high sequence identity with their identified orthologues. MFSD4A and MFSD9 also shared more than 20% sequence identity with other phylogenetically related SLC and MFSD proteins, allowing new family clustering. Homology models displayed 12 transmembrane segments for both proteins, which were predicted to fold into a transporter-shaped structure. Furthermore, we analysed the location of MFSD4A and MFSD9 in adult mouse brain using immunohistochemistry, showing abundant neuronal protein staining. As MFSD4A and MFSD9 are plausible transporters expressed in food regulatory brain areas, we monitored transcriptional changes in several mouse brain areas after 24 hours food-deprivation and eight weeks of high-fat diet, showing that both genes were affected by altered food intake in vivo. In conclusion, we propose MFSD4A and MFSD9 to be novel transporters, belonging to disparate SLC families. Both proteins were located to neurons in mouse brain, and their mRNA expression levels were affected by the diet.

MeSH terms

  • Animals
  • Brain / metabolism*
  • Humans
  • Immunohistochemistry
  • Membrane Transport Proteins / chemistry
  • Membrane Transport Proteins / genetics
  • Membrane Transport Proteins / metabolism*
  • Mice
  • Phylogeny
  • Protein Conformation
  • RNA, Messenger / genetics

Substances

  • MFSD4A protein, human
  • Membrane Transport Proteins
  • RNA, Messenger

Grants and funding

This work was supported by the Swedish Research Council, Swedish Brain Foundation, Novo Nordisk Foundation, Gunvor and Josef Anérs Foundation, Magnus Bergvalls Foundation, Tore Nilssons Foundation and Åhléns Foundation. We have received funding from the Novo Nordisk Foundation, but this does not alter our adherence to PLOS ONE policies on sharing data and materials.