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Ca2+ channel activation by platelet-derived growth factor-induced tyrosine phosphorylation and Ras guanine

H Ma1, H Matsunaga, B Li

  • 1Department of Medicine, Renal Division, Emory University School of Medicine, Altanta, Georgia 30322, USA.

The Journal of Clinical Investigation
|May 15, 1996
PubMed

Insights

Platelet-derived growth factor (PDGF) activates 1-pS Ca2+ channels in rat mesangial cells via a pathway involving tyrosine kinase and Ras activation. This signaling cascade is crucial for cellular responses.

Area of Science:

  • Cellular signaling
  • Molecular biology
  • Physiology

Background:

  • Platelet-derived growth factor (PDGF) plays a critical role in regulating mesangial cell function.
  • Calcium (Ca2+) channels are essential for various cellular processes, including proliferation and contraction.
  • Understanding the specific signaling pathways activated by PDGF is key to elucidating mesangial cell behavior.

Purpose of the Study:

  • To investigate the signaling mechanisms by which PDGF activates 1-pS Ca2+ channels in cultured rat mesangial cells.
  • To identify the key molecular players involved in PDGF-mediated 1-pS Ca2+ channel activation.
  • To determine the role of tyrosine kinase and GTP-binding proteins in this signaling pathway.

Main Methods:

  • Patch-clamp electrophysiology was used to measure 1-pS Ca2+ channel activity in cell-attached and excised patches.
  • Pharmacological inhibitors of tyrosine kinase (genistein, tryphostin 9) and GTP-binding proteins (GTPgammaS, GDPbetaS, pertussis toxin) were employed.
  • Specific antibodies against Ras and western immunoblotting were used to detect protein complex formation.

Main Results:

  • PDGF-BB significantly stimulated 1-pS Ca2+ channel activity in mesangial cells.
  • Tyrosine kinase inhibition abolished PDGF-induced channel activation, an effect reversible by GTPgammaS but not GDPbetaS.
  • Anti-Ras antibody blocked PDGF-induced channel activity, and western blots confirmed PDGF-BB induced a complex of growth factor receptor-binding protein 2, son of sevenless, and PDGF-beta receptor.

Conclusions:

  • The intrinsic tyrosine kinase activity of the PDGF-beta receptor initiates signaling.
  • This leads to the formation of a membrane-bound complex involving growth factor receptor-binding protein 2 and son of sevenless.
  • Activation of the pertussis toxin-insensitive GTP-binding protein, p21-Ras, ultimately gates the 1-pS Ca2+ channels.

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