Sphingosine 1-Phosphate Receptor 5 (S1P5) Deficiency Promotes Proliferation and Immortalization of Mouse Embryonic...

Area of Science:

• Cell Biology
• Molecular Biology
• Lipid Signaling

Background:

• Sphingosine 1-phosphate (S1P) is a bioactive lipid that signals through five G protein-coupled receptors (S1P1-5).
• The precise role of S1P receptor 5 (S1P5) in regulating cell proliferation, particularly in untransformed cells, is not fully understood.
• Existing data on S1P5's function in cell proliferation are often contradictory.

Purpose of the Study:

• To investigate the impact of S1P5 deficiency on the morphology and proliferation of mouse embryonic fibroblasts (MEFs).
• To elucidate the underlying molecular mechanisms by which S1P5 influences cell growth and behavior.
• To clarify the role of S1P5 in counteracting the growth-promoting effects of other S1P receptors.

Main Methods:

• Generation and analysis of S1P5-deficient mouse embryonic fibroblasts (MEFs).
• Assessment of cell morphology, proliferation rates, senescence, spreading, and migration.
• Investigation of downstream signaling pathways, including FAK and ERK activation.
• Rescue experiments involving the reintroduction of exogenous S1P5.

Main Results:

• S1P5 deficiency significantly altered MEF morphology, decreasing cell size and promoting elongation.
• Lack of S1P5 reduced cellular senescence and enhanced MEF immortalization.
• Proliferation rate increased in S1P5-deficient cells, a phenotype reversed by S1P5 reintroduction.
• Mechanistically, S1P5 promotes FAK activation for cell adhesion and spreading, and its anti-proliferative effect involves reduced nuclear ERK activation.

Conclusions:

• S1P5 plays a critical role in controlling cell morphology and proliferation in MEFs.
• S1P5 acts as a tumor suppressor by inhibiting cell growth and promoting adhesion.
• S1P5 opposes the proliferative signals of S1P1-3 through spatial regulation of ERK, providing novel insights into S1P signaling.