Cytoplasmic targeting of the proto-oncogene SET promotes cell spreading and migration

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• The RhoGTPase Rac1 regulates cell motility and is activated in a polarized manner.
• Previous research indicated Rac1 binds to the PP2A inhibitor SET, translocating it to the cytosol.
• The role of SET in regulating cell motility and its interaction with Rac1 requires further elucidation.

Purpose of the Study:

• To investigate the function of a SET mutant lacking a nuclear localization signal (SET(ΔNLS)) in cell motility.
• To determine the effects of SET(ΔNLS) on cell spreading, membrane ruffling, and associated signaling pathways.
• To explore the relationship between SET, Rac1, and the mitogen-activated protein kinases ERK1/ERK2.

Main Methods:

• Expression of wild-type SET and a SET mutant (SET(ΔNLS)) in cells.
• Assessment of cell spreading and motility.
• Quantification of membrane ruffles.
• Pharmacological inhibition of Protein Phosphatase 2A (PP2A).
• Analysis of ERK1 and ERK2 protein levels.

Main Results:

• SET(ΔNLS) expression significantly promoted cell spreading and motility.
• Increased numbers and frequency of membrane ruffles were observed upon SET(ΔNLS) expression.
• Pharmacological inhibition of PP2A did not replicate the effects of SET(ΔNLS).
• Expression of both SET and SET(ΔNLS) led to elevated levels of ERK1 and ERK2.

Conclusions:

• SET, particularly when localized outside the nucleus, plays a crucial role in promoting cell motility and membrane dynamics.
• The observed effects of SET(ΔNLS) on cell motility are not solely mediated by PP2A inhibition.
• SET and its nuclear-excluded form influence the activation or stability of ERK1/ERK2, suggesting a role in Rac1-mediated signaling pathways that control cell behavior.