Molecular determinants for differential membrane trafficking of PMCA1 and PMCA2 in mammalian hair cells

J Cell Sci. 2006 Jul 15;119(Pt 14):2995-3007. doi: 10.1242/jcs.03030. Epub 2006 Jun 27.

Abstract

The plasma membrane Ca2+-ATPase-2 (PMCA2) is expressed in stereocilia of hair cells of the inner ear, whereas PMCA1 is expressed in the basolateral plasma membrane of hair cells. Both extrude excess Ca2+ from the cytosol. They are predicted to contain ten membrane-spanning segments, two large cytoplasmic loops as well as cytosolic N- and C-termini. Several isoform variants are generated for both PMCA1 and PMCA2 by alternative splicing, affecting their first cytosolic loop (A-site) and their C-terminal tail. To understand how these isoforms are differentially targeted in hair cells, we investigated their targeting regions and expression in hair cells. Our results show that a Leu-Ile motif in 'b'-tail splice variants promotes PMCA1b and PMCA2b basolateral sorting in hair cells. Moreover, apical targeting of PMCA2 depends on the size of the A-site-spliced insert, suggesting that the conformation of the cytoplasmic loop plays a role in apical targeting.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural

MeSH terms

  • Amino Acid Motifs
  • Amino Acid Sequence
  • Animals
  • Cell Membrane / metabolism*
  • Cells, Cultured
  • Clone Cells
  • DNA, Complementary / isolation & purification
  • Dogs
  • Epithelial Cells / cytology
  • Hair Cells, Auditory / cytology*
  • Hair Cells, Auditory / enzymology
  • Hair Cells, Auditory / metabolism*
  • Humans
  • Isoleucine / metabolism
  • Leucine / metabolism
  • Molecular Sequence Data
  • Molecular Weight
  • Plasma Membrane Calcium-Transporting ATPases / chemistry
  • Plasma Membrane Calcium-Transporting ATPases / genetics
  • Plasma Membrane Calcium-Transporting ATPases / metabolism*
  • Protein Isoforms
  • Protein Transport
  • Rats
  • Swine

Substances

  • DNA, Complementary
  • Protein Isoforms
  • Isoleucine
  • Plasma Membrane Calcium-Transporting ATPases
  • Leucine