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Updated: Oct 19, 2025

Isolation of Peritoneum-derived Mast Cells and Their Functional Characterization with Ca2+-imaging and Degranulation Assays
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Isolation of Peritoneum-derived Mast Cells and Their Functional Characterization with Ca2+-imaging and Degranulation Assays

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RACK1 plays a critical role in mast cell secretion and Ca2+ mobilization by modulating F-actin dynamics

Edismauro G Freitas Filho1, Elaine Z M da Silva1, Hwei Ling Ong2

  • 1Department of Cell and Molecular Biology and Pathogenic Bioagents, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Av. Bandeirantes 3900, Ribeirão Preto, SP 14049-900, Brazil.

Journal of Cell Science
|September 22, 2021
PubMed

Insights

Receptor for activated C kinase 1 (RACK1) regulates mast cell (MC) actin dynamics and calcium signaling. RACK1 knockdown in MCs disrupts actin organization, enhances degranulation, and alters calcium mobilization.

Area of Science:

  • Immunology
  • Cell Biology
  • Biochemistry

Background:

  • Receptor for activated C kinase 1 (RACK1) is a known signaling hub in immune cells.
  • Its specific role and presence within mast cells (MCs) remain uncharacterized.
  • Mast cell activation involves cytoskeleton reorganization and calcium (Ca2+) flux.

Purpose of the Study:

  • To investigate the presence and function of RACK1 in mast cells.
  • To determine RACK1's role in MC activation, mediator release, and calcium signaling.

Main Methods:

  • RACK1 knockdown (KD) in mast cells (in vivo and in vitro).
  • Analysis of actin dynamics (F-actin and G-actin) and cytoskeleton organization.
  • Assessment of degranulation and secretory granule localization (CD63+).
  • Measurement of intracellular calcium mobilization and endoplasmic reticulum (ER) Ca2+ store depletion.
  • Investigation of RACK1 interactions with Orai1, β-actin, vinculin, and MyoVa.

Main Results:

  • RACK1 is present throughout the cytoplasm of mast cells.
  • RACK1 knockdown led to rounded MCs with fragmented cortical F-actin and impaired actin organization upon stimulation.
  • RACK1 KD increased and accelerated degranulation, with secretory granules localized in actin-free regions.
  • RACK1 KD enhanced antigen-stimulated Ca2+ mobilization but attenuated ER Ca2+ store depletion and Ca2+ entry.
  • RACK1 interacts with Orai1 Ca2+-channels, β-actin, vinculin, and MyoVa during MC activation.

Conclusions:

  • RACK1 is a critical regulator of actin dynamics in mast cells.
  • RACK1 influences mast cell mediator secretion and calcium signaling pathways.
  • RACK1 plays a key role in mast cell activation processes.

Keywords:
Actin cytoskeletonDegranulationMast cellsRACK1Store-operated Ca2+ entry

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