Shoc2 is targeted to late endosomes and required for Erk1/2 activation in EGF-stimulated cells

Area of Science:

• Cellular Biology
• Molecular Signaling
• Signal Transduction

Background:

• Shoc2 acts as a scaffold protein, interacting with RAS and RAF to regulate extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) signaling.
• The precise mechanism by which Shoc2 influences ERK1/2 activation, particularly in response to epidermal growth factor receptor (EGFR) signaling, remains incompletely understood.

Purpose of the Study:

• To investigate the subcellular localization of Shoc2 during EGFR activation.
• To elucidate the role of Shoc2's localization in regulating ERK1/2 activation by EGFR.

Main Methods:

• Studied the subcellular localization of endogenous and fluorescently tagged Shoc2 upon EGFR activation.
• Utilized overexpression of RAS mutants and RNA interference (RNAi) for clathrin knockdown to assess Shoc2 recruitment.
• Employed RNAi to deplete Shoc2 and assessed ERK1/2 activation rescue with wild-type and mutant Shoc2 expression.

Main Results:

• EGFR activation induced Shoc2 translocation from the cytosol to Rab7-positive late endosomes.
• Shoc2 recruitment to endosomes required RAS activity and clathrin-dependent endocytosis.
• Shoc2 depletion inhibited ERK1/2 activation at low EGF concentrations, with rescue by wild-type Shoc2.
• A myristoylated Shoc2 mutant (S2G), associated with Noonan-like syndrome, failed to rescue ERK1/2 activation and localized to the plasma membrane and early endosomes, not late endosomes.

Conclusions:

• Shoc2 targeting to late endosomes is essential for facilitating EGFR-induced ERK activation under physiological conditions.
• Shoc2's spatiotemporal regulation of the RAS-RAF signaling module is critical for effective cellular responses to EGF.
• Dysregulation of Shoc2 localization, as seen with the S2G mutant, may contribute to developmental disorders like Noonan-like syndrome.