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Molecular Basis for Inhibition of the Na+/Citrate Transporter NaCT (SLC13A5) by Dicarboxylate Inhibitors

Ana M Pajor1, Cesar A de Oliveira2, Kun Song2

  • 1University of California San Diego (A.M.P.), Skaggs School of Pharmacy and Pharmaceutical Sciences, La Jolla, California; Cardiovascular, Metabolic and Endocrine Disease Research Unit (K.S., K.H., D.M.E.), Pfizer Worldwide Research and Development, Cambridge, Massachusetts; Center of Chemistry Innovation and Excellence (C.A.O., V.S.), Pfizer Worldwide Research and Development, Groton, Connecticut apajor@ucsd.edu.

Molecular Pharmacology
|September 30, 2016
PubMed

Insights

Researchers investigated the Na+/citrate transporter (NaCT) and its inhibitors. Key residues affecting citrate transport and drug binding were identified, paving the way for improved metabolic disease therapies.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Pharmacology

Background:

  • The Na+/citrate transporter (NaCT, SLC13A5) is crucial for metabolic regulation and a target for treating metabolic diseases.
  • Citrate acts as a signaling molecule influencing lipid and glucose metabolism.
  • Previous research identified two high-affinity NaCT inhibitors, PF-06649298 and PF-06678419.

Purpose of the Study:

  • To elucidate the molecular mechanisms of NaCT inhibition and transport.
  • To identify specific amino acid residues involved in inhibitor binding and substrate transport.
  • To provide a foundation for designing novel SLC13 inhibitors.

Main Methods:

  • Molecular modeling of human NaCT (hNaCT).
  • Site-directed mutagenesis of hNaCT residues.
  • Transport assays to characterize citrate uptake.
  • Cell-surface biotinylation to assess protein localization.

Main Results:

  • Residues G228, V231, V232, and G409 near the citrate binding site impact both transport and inhibitor binding.
  • Residue V231 differentiates the inhibitory effects of PF-06649298 and PF-06678419.
  • Residues Q77 and T86, outside the putative citrate site, also influence NaCT inhibition.

Conclusions:

  • Specific residues within and outside the citrate binding pocket are critical for NaCT function and inhibition.
  • Understanding these interactions advances knowledge of NaCT transport mechanisms.
  • These findings support the rational design of NaCT-targeting drugs for metabolic disorders.

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