A clathrin-dependent pathway leads to KRas signaling on late endosomes en route to lysosomes

Area of Science:

• Cell Biology
• Molecular Biology
• Signal Transduction

Background:

• Ras proteins are key regulators of cellular functions including proliferation and differentiation.
• Understanding Ras intracellular trafficking is vital for identifying novel signaling platforms.

Purpose of the Study:

• To investigate the intracellular trafficking and signaling of Kirsten Ras (KRas) in response to epidermal growth factor (EGF).
• To identify the specific endosomal compartments involved in KRas signaling and its downstream effectors.

Main Methods:

• Utilized clathrin-dependent pathways for KRas translocation.
• Employed yellow fluorescent protein-Raf1 and Raichu-KRas probes for in vivo imaging.
• Investigated KRas localization on Rab7-positive late endosomes (LEs).

Main Results:

• EGF induces KRas translocation to endosomal membranes via a clathrin-dependent pathway.
• KRas is sorted from early endosomes to LEs and lysosomes, unlike other Ras isoforms.
• Active KRas was identified on Rab7 LEs, signaling through Raf1 and involving the p14-MP1 complex and ERK1/2.
• Inhibition of lysosomal function resulted in prolonged signaling from LEs.

Conclusions:

• This study elucidates novel aspects of KRas intracellular trafficking and signaling.
• KRas signaling occurs on late endosomes, influencing mitogen-activated protein kinase pathways.
• Findings provide new insights into the regulatory mechanisms controlling Ras in cellular processes.