Determinants in the β and δ subunit cytoplasmic loop regulate Golgi trafficking and surface expression of the muscle acetylcholine receptor

Jolene Chang Rudell, Lucia S. Borges, John B. Rudell, Kenneth A Beck, Michael J Ferns

Research output: Contribution to journalArticle

6 Scopus citations

Abstract

The molecular determinants that govern nicotinic acetylcholine receptor (AChR) assembly and trafficking are poorly defined, and those identified operate largely during initial receptor biogenesis in the endoplasmic reticulum. To identify determinants that regulate later trafficking steps, we performed an unbiased screen using chimeric proteins consisting of CD4 fused to the muscle AChR subunit cytoplasmic loops. In C2 mouse muscle cells, we found that CD4-β and δ subunit loops were expressed at very low levels on the cell surface, whereas the other subunit loops were robustly expressed on the plasma membrane. The low surface expression of CD4-β and δ loops was due to their pronounced retention in the Golgi apparatus and also to their rapid internalization from the plasma membrane. Both retention and recovery were mediated by the proximal 25-28 amino acids in each loop and were dependent on an ordered sequence of charged and hydrophobic residues. Indeed, βK353L and δK351L mutations increased surface trafficking of the CD4-subunit loops by >6-fold and also decreased their internalization from the plasma membrane. Similarly, combined βK353L and δK351L mutations increased the surface levels of assembled AChR expressed in HEK cells to 138% of wildtype levels. This was due to increased trafficking to the plasma membrane and not decreased AChR turnover. These findings identify novel Golgi retention signals in the β and δ subunit loops that regulate surface trafficking of assembled AChR and may help prevent surface expression of unassembled subunits. Together, these results define molecular determinants that govern a Golgi-based regulatory step in nicotinic AChR trafficking.

Original languageEnglish (US)
Pages (from-to)203-214
Number of pages12
JournalJournal of Biological Chemistry
Volume289
Issue number1
DOIs
StatePublished - Jan 3 2014

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology
  • Molecular Biology

Fingerprint Dive into the research topics of 'Determinants in the β and δ subunit cytoplasmic loop regulate Golgi trafficking and surface expression of the muscle acetylcholine receptor'. Together they form a unique fingerprint.

  • Cite this