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v-Src-induced modulation of the calpain-calpastatin proteolytic system regulates transformation

N O Carragher1, M A Westhoff, D Riley

  • 1The Beatson Institute for Cancer Research, Cancer Research Campaign Beatson Laboratories, Glasgow, Scotland, United Kingdom. n.carragher@beatson.gla.ac.uk

Molecular and Cellular Biology
|December 12, 2001
PubMed

Insights

The calpain-calpastatin system drives v-Src oncogenic transformation by degrading focal adhesion kinase (FAK) and promoting cell cycle progression. Restoring calpastatin levels inhibits these effects, highlighting its role in cancer development.

Area of Science:

  • Cell Biology
  • Molecular Oncology
  • Biochemistry

Background:

  • v-Src oncogene induces significant cellular changes, including altered morphology, adhesion, and proliferation.
  • The calpain-calpastatin system is a key regulator of cellular processes, involving calcium-dependent proteases and their inhibitors.

Purpose of the Study:

  • To investigate the role of the calpain-calpastatin system in v-Src-induced oncogenic transformation.
  • To elucidate the signaling pathways downstream of v-Src involving calpains and calpastatin.

Main Methods:

  • Studied the effects of v-Src on calpain II synthesis and calpastatin degradation in chicken embryo fibroblasts.
  • Utilized overexpression of exogenous calpastatin to assess its impact on FAK cleavage and cell transformation.
  • Analyzed cell cycle progression, pRb phosphorylation, and cyclin levels in v-Src-transformed cells with altered calpastatin levels.
  • Examined v-Src-induced transformation in calpain 4 knockout fibroblasts.

Main Results:

  • v-Src activation leads to increased calpain II synthesis and degradation of calpastatin, forming a positive feedback loop.
  • Overexpression of calpastatin suppressed FAK cleavage, morphological transformation, and anchorage-independent growth.
  • Calpastatin overexpression inhibited G1 cell cycle progression, reducing pRb phosphorylation and cyclin levels.
  • Calpain 4 knockout cells showed impaired v-Src-induced transformation.

Conclusions:

  • The calpain-calpastatin proteolytic system is crucial for v-Src-induced oncogenic transformation.
  • Modulation of this system impacts focal adhesion disassembly, cell morphology, and cell cycle progression.
  • Targeting the calpain-calpastatin system may offer therapeutic strategies against v-Src-driven cancers.

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