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Kinase-dependent adhesion to fibronectin: regulation by calreticulin

Sylvia Papp1, Eva Szabo, Hugh Kim

  • 1Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada.

Experimental Cell Research
|February 8, 2008
PubMed

Insights

Calreticulin deficiency impairs cell adhesion and fibronectin deposition by altering c-Src and CaMKII activity. Restoring calreticulin or fibronectin improves cell spreading and focal contact formation.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Calreticulin is a key endoplasmic reticulum chaperone involved in protein folding and calcium homeostasis.
  • Cellular adhesion and spreading are critical processes regulated by intricate signaling pathways.
  • The role of calreticulin in modulating cell-matrix interactions and associated signaling remains incompletely understood.

Purpose of the Study:

  • To investigate the role of calreticulin in regulating cell adhesion, focal contact formation, and the activity of c-Src and CaMKII signaling pathways.
  • To determine whether calreticulin's calcium-binding function influences these cellular processes.

Main Methods:

  • Studied phosphorylation of c-Src and CaMKII in wild-type, calreticulin-null, and rescued MEFs.
  • Assessed cell spreading, focal contact formation, and fibronectin expression.
  • Utilized fibronectin plating, c-Src, calmodulin, and CaMKII inhibition.
  • Manipulated intracellular calcium levels to assess calreticulin's calcium storage function.

Main Results:

  • Calreticulin-null MEFs exhibited poor cell spreading, reduced focal contacts, and lower fibronectin expression.
  • Calreticulin deficiency led to increased c-Src and CaMKII phosphorylation.
  • Restoring fibronectin or inhibiting c-Src, calmodulin, or CaMKII rescued the defective cell spreading phenotype.
  • Altering intracellular calcium levels modulated c-Src phosphorylation and fibronectin abundance.

Conclusions:

  • Calreticulin is essential for proper cell spreading and focal contact formation, mediated through regulation of fibronectin deposition.
  • Calreticulin influences the activity of both c-Src and calmodulin/CaMKII signaling pathways.
  • Calreticulin's calcium storage function contributes to the regulation of these signaling pathways and cellular adhesion.

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