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Rab3 proteins involved in vesicle biogenesis and priming in embryonic mouse chromaffin cells

Jean-Sébastien Schonn1, Jan R T van Weering, Ralf Mohrmann

  • 1Membrane biophysics, Max-Planck-Institute for Biophysical Chemistry, Am Fassberg 11, D-37077 Göttingen, Germany.

Traffic (Copenhagen, Denmark)
|August 19, 2010
PubMed

Insights

Rab3 proteins are crucial for exocytosis in chromaffin cells. Deleting all four Rab3 paralogs impairs vesicle release by affecting biogenesis and priming, but not fusion kinetics.

Area of Science:

  • Cell Biology
  • Neuroscience
  • Molecular Biology

Background:

  • Rab3 proteins (A-D) are implicated in exocytosis.
  • Functional redundancy among Rab3 paralogs complicates studying their individual roles.

Purpose of the Study:

  • Investigate the function of Rab3 proteins in exocytosis using a quadruple knockout mouse model.
  • Elucidate the specific roles of Rab3 proteins in vesicle priming and fusion in adrenal chromaffin cells.

Main Methods:

  • Generated a quadruple Rab3 knockout (ABCD(-/-)) mouse line.
  • Utilized electron microscopy and electrophysiological measurements (capacitance assays) on embryonic adrenal chromaffin cells.
  • Performed rescue experiments with Rab3A and Rab3C overexpression.

Main Results:

  • ABCD(-/-) cells showed reduced large dense-core vesicle (LDCV) abundance but normal docked granule numbers.
  • Rab3 deletion decreased the releasable vesicle pool size without altering fusion kinetics.
  • Vesicle priming in ABCD(-/-) cells exhibited a delayed but faster sustained release rate.
  • Short-term Rab3A/C overexpression rescued priming and secretion but not vesicle number.

Conclusions:

  • Rab3 proteins play dual roles in LDCV fusion: facilitating vesicle biogenesis and stabilizing the primed vesicle state.
  • These findings highlight distinct functions of Rab3 proteins in regulating exocytosis.
  • Rab3 proteins are essential for efficient secretory vesicle dynamics in chromaffin cells.

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