SLC26A4-AP-2 mu2 interaction regulates SLC26A4 plasma membrane abundance in the endolymphatic sac

Sci Adv. 2024 Oct 11;10(41):eadm8663. doi: 10.1126/sciadv.adm8663. Epub 2024 Oct 9.

Abstract

Decreased presence or activity of human SLC26A4 at the plasma membrane is a common cause of hearing loss. SLC26A4 (Pendrin) is necessary for normal reabsorption of endolymph, the fluid bathing the inner ear. We identified the μ2 subunit of adaptor protein 2 (AP-2) complex required for clathrin-mediated endocytosis as a protein-partner of SLC26A4 involved in regulating its plasma membrane abundance. We showed that, in the endolymphatic sac, where fluid reabsorption occurs, SLC26A4 is localized along the apical microvilli of mitochondria-rich cells, in contact with the endolymph, and associated with clathrin-coated pits where μ2 and AP-2 are present. Based on SLC26A4 structure, the elements involved in SLC26A4-μ2 interaction were identified and validated experimentally, allowing modeling of this interaction at the atomic level. Pharmacological inhibition of clathrin-mediated endocytosis led to an increased plasma membrane abundance of hemagglutinin-tagged SLC26A4 virally or endogenously expressed in mitochondria-rich cells. These results indicate that the SLC26A4-μ2 interaction regulates SLC26A4 abundance at the apical surface of mitochondria-rich cells.

MeSH terms

  • Adaptor Protein Complex 2* / metabolism
  • Animals
  • Cell Membrane* / metabolism
  • Clathrin / metabolism
  • Endocytosis*
  • Endolymphatic Sac* / metabolism
  • Humans
  • Mice
  • Mitochondria / metabolism
  • Protein Binding
  • Sulfate Transporters* / genetics
  • Sulfate Transporters* / metabolism

Substances

  • Adaptor Protein Complex 2
  • Clathrin
  • SLC26A4 protein, human
  • Sulfate Transporters
  • adaptor protein complex 2, mu 2 subunit