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Myosin 5a controls insulin granule recruitment during late-phase secretion

Rosita Ivarsson1, Xingjun Jing, Laurent Waselle

  • 1Department of Experimental Medical Science, Lund University, Lund, Sweden.

Traffic (Copenhagen, Denmark)
|September 30, 2005
PubMed

Insights

Myosin 5a is crucial for insulin secretion, transporting insulin granules via the actin network. Inhibiting this motor significantly reduces hormone release and granule exocytosis.

Area of Science:

  • Cell Biology
  • Molecular Physiology
  • Endocrinology

Background:

  • Insulin secretion relies on the transport of insulin granules to the plasma membrane.
  • The role of specific molecular motors in this process remains incompletely understood.

Purpose of the Study:

  • To investigate the function of the actin-based motor myosin 5a in insulin granule transport and secretion.
  • To elucidate the mechanism linking myosin 5a to insulin granules.

Main Methods:

  • RNA interference (RNAi) to downregulate myosin 5a and Slac-2c/MYRIP expression in INS-1E cells.
  • Measurement of stimulated hormone secretion and single-cell exocytosis using capacitance recordings.
  • Antibody inhibition of myosin 5a-Slac-2c/MYRIP interaction.
  • Total internal reflection fluorescence microscopy (TIR-FM) to visualize granule dynamics.

Main Results:

  • Downregulation of myosin 5a reduced stimulated hormone secretion by 46% and single-cell exocytosis by 42%.
  • Silencing of Slac-2c/MYRIP, a myosin 5a linker, similarly inhibited exocytosis.
  • Myosin 5a inhibition impaired late-phase granule recruitment to the plasma membrane.
  • An estimated 550 granules constitute the releasable pool independent of myosin 5a.

Conclusions:

  • Myosin 5a is essential for efficient insulin granule transport and secretion.
  • Slac-2c/MYRIP acts as a crucial link between insulin granules and myosin 5a.
  • Insulin granules utilize both myosin 5a-dependent and passive transport mechanisms, with myosin 5a dominating under stimulation.

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