VPS34 regulates TSC1/TSC2 heterodimer to mediate RheB and mTORC1/S6K1 activation and cellular transformation

Area of Science:

• Cell Biology
• Molecular Oncology
• Signal Transduction

Background:

• VPS34 (Vacuolar protein sorting 34) is known to activate S6K1 and influence cell growth, but its precise regulatory mechanisms are unclear.
• Understanding VPS34's role is crucial for deciphering cell growth regulation and its implications in cancer.

Purpose of the Study:

• To elucidate the novel mechanisms by which VPS34 regulates mTOR/S6K1 activity and cell growth.
• To investigate the role of VPS34 in oncogenic transformation.

Main Methods:

• Investigated VPS34-mediated regulation of TSC2 protein levels and RheB activity.
• Utilized lipid kinase activity assays and protein complex formation studies.
• Employed site-directed mutagenesis (H868R) to probe VPS34 function and kinase-dead mutants to confirm specificity.

Main Results:

• VPS34 upregulates mTOR/S6K1 by decreasing TSC2 protein levels and activating RheB.
• Increased VPS34 lipid kinase activity enhances PIKFYVE and TSC1 recruitment to the plasma membrane, promoting TSC2 ubiquitination and degradation.
• VPS34 activity drives oncogenic transformation, while kinase-dead mutants abolish these effects.

Conclusions:

• VPS34 promotes oncogenic transformation through a novel pathway involving TSC2 downregulation and mTOR/S6K1 activation.
• This study provides mechanistic insights into VPS34's function and highlights its potential as a target for cancer therapies.
• Findings suggest the importance of identifying VPS34 mutations in human cancers.