Post-translational membrane insertion of tail-anchored transmembrane EF-hand Ca2+ sensor calneurons requires the TRC40/Asna1 protein chaperone

Johannes Hradsky, Vijeta Raghuram, Parameshwar Pasham Reddy, Gemma Navarro, Mike Hupe, Vicent Casado, Peter J McCormick, Yogendra Sharma, Michael R Kreutz, Marina Mikhaylova

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25 Citations (Scopus)


Calneuron-1 and -2 are neuronal EF-hand-type calcium sensor proteins that are prominently targeted to trans-Golgi network membranes and impose a calcium threshold at the Golgi for phosphatidylinositol 4-OH kinase IIIβ activation and the regulated local synthesis of phospholipids that are crucial for TGN-to-plasma membrane trafficking. In this study, we show that calneurons are nonclassical type II tail-anchored proteins that are post-translationally inserted into the endoplasmic reticulum membrane via an association of a 23-amino acid-long transmembrane domain (TMD) with the TRC40/Asna1 chaperone complex. Following trafficking to the Golgi, calneurons are probably retained in the TGN because of the length of the TMD and phosphatidylinositol 4-phosphate lipid binding. Both calneurons rapidly self-associate in vitro and in vivo via their TMD and EF-hand containing the N terminus. Although dimerization and potentially multimerization precludes TRC40/Asna1 binding and thereby membrane insertion, we found no evidence for a cytosolic pool of calneurons and could demonstrate that self-association of calneurons is restricted to membrane-inserted protein. The dimerization properties and the fact that they, unlike every other EF-hand calmodulin-like Ca(2+) sensor, are always associated with membranes of the secretory pathway, including vesicles and plasma membrane, suggests a high degree of spatial segregation for physiological target interactions.
Original languageEnglish
Pages (from-to)36762-76
Number of pages15
JournalThe Journal of Biological Chemistry
Issue number42
Publication statusPublished - 21 Oct 2011


  • Animals
  • Arsenite Transporting ATPases
  • COS Cells
  • Calcium
  • Calmodulin
  • Cercopithecus aethiops
  • HEK293 Cells
  • HeLa Cells
  • Humans
  • Intracellular Membranes
  • Molecular Chaperones
  • Protein Multimerization
  • Protein Structure, Tertiary
  • Protein Transport
  • trans-Golgi Network

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