Actuation of single downstream nodes in growth factor network steers immune cell migration

Area of Science:

• Cell Biology
• Molecular Biology
• Biophysics

Background:

• Ras signaling is primarily linked to cell growth.
• Its direct role in regulating cell motility and polarity is not well understood.
• Chemoattractant receptors and G-protein networks typically control cell migration.

Purpose of the Study:

• To investigate the direct role of Ras signaling in regulating cell motility and polarity.
• To explore the impact of optogenetically activating specific nodes within the Ras/PI3K/Akt network on cell behavior.
• To determine if Ras signaling can bypass traditional chemoattractant pathways to control cell migration.

Main Methods:

• Optogenetic targeting of Ras/PI3K/Akt network components in human HL-60 neutrophils and murine RAW 264.7 macrophages.
• Manipulating Ras isoforms, RasGEFs (RasGRP4), RasGAPs (RASAL3), and Akt recruitment.
• Analyzing changes in cell spreading, random motility, protrusion formation, polarity, and directed migration under chemoattractant gradients.

Main Results:

• Global activation of KRas4B/HRas or RasGRP4 increased cell spreading and random motility.
• Activating Ras at the cell rear induced protrusions, reversed polarity, and steered migration in neutrophils and macrophages.
• Recruiting RASAL3 to cell fronts inhibited protrusions and altered migration direction, even abrogating directed migration in gradients.
• Local Akt activation generated protrusions and rearranged polarity, with effects being mTORC2-dependent but PI3K-independent.

Conclusions:

• Receptor-independent, local activation of Ras signaling pathways directly controls actin assembly, cell shape, and migration modes.
• Classical growth-control pathways can bypass chemoattractant receptor networks to regulate cell motility.
• The Ras/Akt pathway, particularly via mTORC2, plays a significant role in cell migration dynamics.