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Epidermal growth factor induces tyrosine phosphorylation, membrane insertion, and activation of transient receptor

Adam F Odell1, Judith L Scott, Dirk F Van Helden

  • 1School of Biomedical Sciences, Level 5 MSB, University of Newcastle, Callaghan, New South Wales, Australia. adam.odell@newcastle.edu.au

The Journal of Biological Chemistry
|September 8, 2005
PubMed

Insights

This study reveals how epidermal growth factor (EGF) receptor stimulation triggers tyrosine phosphorylation of the transient receptor potential channel 4 (TRPC4). This phosphorylation, mediated by Src family tyrosine kinases, enhances TRPC4 channel activity and calcium influx.

Area of Science:

  • Molecular Biology
  • Cell Signaling
  • Ion Channel Physiology

Background:

  • Transient receptor potential channels (TRPCs) regulate cation influx, crucial for cellular functions.
  • Tyrosine phosphorylation is known to modulate TRPC activity, but the underlying mechanism remains elusive.

Purpose of the Study:

  • To elucidate the mechanism linking receptor stimulation, tyrosine phosphorylation, and TRPC4 channel activity.
  • To identify specific tyrosine residues and kinases involved in TRPC4 regulation.

Main Methods:

  • Utilized COS-7 and HEK293 cell lines, epidermal growth factor (EGF) stimulation, and Src family tyrosine kinase (STK) inhibitors.
  • Employed site-directed mutagenesis to alter specific tyrosine residues (Tyr-959 and Tyr-972) in human TRPC4 (hTRPC4).
  • Assessed hTRPC4 phosphorylation, plasma membrane translocation, association with Na(+)/H(+) exchanger regulatory factor, and Ca(2+) influx.

Main Results:

  • EGF receptor stimulation induced phosphorylation of hTRPC4 at Tyr-959 and Tyr-972, mediated by STKs like Fyn.
  • EGF stimulation promoted exocytotic insertion of hTRPC4 into the plasma membrane, dependent on STK activity.
  • Phosphorylation-dependent association of hTRPC4 with Na(+)/H(+) exchanger regulatory factor was observed.
  • Mutating Tyr-959 and Tyr-972 to phenylalanine impaired translocation and association, reducing EGF-induced Ca(2+) influx.

Conclusions:

  • Established a novel mechanism where STK-mediated tyrosine phosphorylation of hTRPC4 at specific sites modulates its channel function.
  • Demonstrated that phosphorylation regulates hTRPC4 translocation and interaction with regulatory proteins, impacting calcium signaling.

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