Renal localization and regulation by dietary phosphate of the MCT14 orphan transporter

Area of Science:

• Molecular Biology
• Renal Physiology
• Membrane Transport

Background:

• Monocarboxylate transporter 14 (MCT14) is an orphan transporter within the SLC16 family.
• Its physiological roles, including expression, localization, regulation, and function, are largely uncharacterized.
• The SLC16 family typically mediates the transport of monocarboxylates, aromatic amino acids, creatine, and thyroid hormones.

Purpose of the Study:

• To investigate the expression, tissue localization, regulation, and function of the orphan transporter MCT14.
• To identify the potential transport substrates of MCT14.
• To understand the physiological relevance of MCT14 in the kidney.

Main Methods:

• Quantitative real-time PCR was used to determine MCT14 mRNA abundance in mouse tissues.
• A newly developed and validated antibody was employed for immunohistochemical localization of MCT14 protein in mouse kidneys.
• MCT14 was expressed in Xenopus laevis oocytes to assess its transport activity for various substrates.

Main Results:

• MCT14 mRNA abundance was highest in the kidney.
• Immunohistochemistry localized MCT14 to the luminal membrane of the thick ascending limb of the loop of Henle, co-localizing with uromodulin and NKCC2.
• MCT14 expression (mRNA and protein) was significantly upregulated by high dietary phosphate intake.
• Functional studies in oocytes did not reveal transport activity for known SLC16 family substrates or phosphate.

Conclusions:

• MCT14 is an orphan transporter highly enriched in the kidney, specifically localized to the luminal membrane of the thick ascending limb.
• Its expression is tightly regulated by dietary phosphate levels.
• Despite its localization and regulation, the specific transport substrates and physiological function of MCT14 remain to be elucidated.