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Cofilin recruits F-actin to SPCA1 and promotes Ca2+-mediated secretory cargo sorting

Christine Kienzle1, Nirakar Basnet1, Alvaro H Crevenna2

  • 1Max Planck Institute of Biochemistry, 82152 Martinsried, Germany.

The Journal of Cell Biology
|September 3, 2014
PubMed

Insights

Cofilin-1 (CFL-1) and actin bind to secretory pathway calcium ATPase 1 (SPCA1), regulating calcium transport and protein sorting at the Golgi. This interaction is crucial for efficient secretory cargo trafficking.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Secretory protein sorting at the trans-Golgi network (TGN) involves calcium regulation.
  • The secretory pathway calcium ATPase 1 (SPCA1) and cofilin-1 (CFL-1) are implicated in this process.
  • The precise mechanism of SPCA1-actin-CFL-1 interaction and its role in cargo sorting remain unclear.

Purpose of the Study:

  • To elucidate the interaction between SPCA1, actin, and CFL-1.
  • To determine how this interaction influences calcium transport and secretory protein sorting at the TGN.

Main Methods:

  • In vitro binding assays using purified SPCA1 cytoplasmic domains, actin, and CFL-1.
  • Affinity purification using SPCA1 P-domain coupled to Ni-NTA agarose beads.
  • Expression of SPCA1 mutants in HeLa cells to assess functional impact.

Main Results:

  • A specific 132-amino acid region of the SPCA1 phosphorylation domain (P-domain) binds actin in a CFL-1-dependent manner.
  • Recruitment of F-actin to SPCA1 via CFL-1 inhibits Ca(2+) influx into the TGN and secretory cargo sorting.
  • Mutagenesis of the identified CFL-1 binding site on SPCA1 disrupts Ca(2+) transport and cargo sorting.

Conclusions:

  • This study reveals the mechanism by which CFL-1 mediates actin recruitment to SPCA1.
  • The SPCA1-actin-CFL-1 interaction is essential for regulating Ca(2+) homeostasis and secretory protein sorting at the TGN.
  • Findings provide insights into the molecular basis of calcium-dependent protein trafficking.

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