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ER/Golgi trafficking is facilitated by unbranched actin filaments containing Tpm4.2

Anthony J Kee1, Nicole S Bryce1, Lingyan Yang1

  • 1School of Medical Sciences, UNSW Sydney, Sydney, NSW 2052, Australia.

Cytoskeleton (Hoboken, N.J.)
|August 24, 2017
PubMed

Insights

Novel actin filaments containing tropomyosin Tpm4.2 are crucial for ER structure and ER-to-Golgi trafficking. These filaments, along with myosin II motors, facilitate vesicle transport, impacting cellular organization.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Cytoskeleton Dynamics

Background:

  • Actin filaments play diverse roles in cellular processes.
  • The specific functions of tropomyosin isoforms, like Tpm4.2, in organelle trafficking are not fully understood.
  • The endoplasmic reticulum (ER) and Golgi apparatus are key for protein processing and transport.

Purpose of the Study:

  • To investigate the role of tropomyosin Tpm4.2-containing actin filaments at the ER.
  • To determine the involvement of these filaments in ER-to-Golgi trafficking.
  • To elucidate the molecular mechanisms underlying ER/Golgi structure maintenance and vesicle transport.

Main Methods:

  • Electron microscopy (EM) analysis of mouse embryo fibroblasts (MEFs) with wild-type and mutant Tpm4.2.
  • Analysis of ER-to-Golgi trafficking using a temperature-sensitive ts045-VSVg construct.
  • Pharmacological inhibition of myosin II (blebbistatin) and Arp2/3-containing filaments (CK666).

Main Results:

  • Mutant Tpm4.2 disrupted actin filament incorporation, leading to swollen ER structures in MEFs.
  • ER-to-Golgi trafficking was impaired in mutant MEFs and rescued by exogenous Tpm4.2.
  • Myosin II inhibition blocked Tpm4.2-dependent ER-to-Golgi trafficking, while Arp2/3 inhibition had no effect.

Conclusions:

  • Unbranched actin filaments containing Tpm4.2 are essential for ER/Golgi structure.
  • Tpm4.2-actin filaments, coupled with myosin II motors, mediate ER-to-Golgi vesicle trafficking.
  • Branched actin filaments are not involved in this specific anterograde trafficking pathway.
Keywords:
actin cytoskeletonmembrane traffickingmyosintropomyosin

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