mTORC1 controls Golgi architecture and vesicle secretion by phosphorylation of SCYL1

Area of Science:

• Cell Biology
• Molecular Biology
• Cancer Research

Background:

• Mechanistic target of rapamycin complex 1 (mTORC1) is a key regulator of cell growth, proliferation, and metabolism.
• mTORC1 hyperactivation is implicated in cancer, driving tumor cell proliferation.
• mTORC1 functions at various subcellular locations, influencing distinct cellular processes.

Purpose of the Study:

• To investigate the role of the N-terminal kinase-like protein SCYL1 as a target of mTORC1.
• To elucidate how mTORC1-SCYL1 signaling impacts organelle distribution and extracellular vesicle secretion in breast cancer.

Main Methods:

• Characterization of SCYL1 localization and phosphorylation status.
• Analysis of Golgi and endosome dynamics upon mTORC1 inhibition.
• Assessment of extracellular vesicle secretion in response to altered SCYL1 phosphorylation.

Main Results:

• mTORC1 phosphorylates SCYL1 at Ser754, promoting its Golgi localization under growth conditions.
• mTORC1 inhibition causes SCYL1 dephosphorylation and redistribution to endosomes.
• Dephosphorylated SCYL1 at the cell periphery leads to Golgi enlargement, endosome redistribution, and increased extracellular vesicle release.

Conclusions:

• The phosphorylation status of SCYL1, regulated by mTORC1, is critical for controlling endolysosomal compartment distribution and function.
• This mTORC1-SCYL1 axis provides insights into breast cancer cell biology and extracellular vesicle release.
• Dysregulation of SCYL1 phosphorylation may contribute to the pathophysiology of genetic disorders like CALFAN syndrome.