S1P induces bleb-based T cell motility via S1PR1-dependent activation of RhoA and WNK1

Area of Science:

• Immunology
• Cell Biology
• Biochemistry

Background:

• Chemokine receptor CCR7 and lipid sphingosine-1-phosphate (S1P) regulate T cell migration.
• CCL19-CCR7 signaling promotes lamellipodial motility, while S1P induces bleb-based motility.

Purpose of the Study:

• To elucidate the molecular mechanisms underlying S1P-driven T cell migration.
• To investigate the signaling pathways activated by S1P receptor 1 (S1PR1) in naïve T cells.

Main Methods:

• Signaling pathway analysis using Gai coupling, Rac1 and RhoA activation assays.
• Investigated myosin light chain (MLC) phosphorylation and contractility.
• Examined the role of mTORC2, WNK1, SPAK1, and OSXR1 in S1P responses.
• Utilized RhoA pathway inhibitors and WNK1 inhibition to assess chemotaxis and blebbing.

Main Results:

• S1P signals via S1PR1 coupled through Gai, leading to transient Rac1 and sustained RhoA activation.
• Sustained RhoA activation enhances myosin contractility via MLC phosphorylation, partly regulated by mTORC2.
• RhoA pathway inhibition did not block S1P-induced chemotaxis, revealing a parallel pathway.
• S1P also activates WNK1, leading to SPAK1/OSXR1 phosphorylation, regulating ion channels and water influx.
• Combined inhibition of myosin contractility and WNK1 blocked S1P-induced blebbing and chemotaxis.

Conclusions:

• S1P-driven T cell migration relies on coordinated activation of myosin contractility and water influx.
• The WNK1-SPAK1/OSXR1 pathway is essential for S1P-mediated chemotaxis and blebbing.
• Understanding these mechanisms provides insights into lymphocyte trafficking and immune responses.