Cis-4-methylsphingosine is a sphingosine-1-phosphate receptor modulator

Area of Science:

• Biochemistry
• Pharmacology
• Cell Biology

Background:

• Sphingosine-1-phosphate (S1P) is a lipid mediator binding to S1P receptors (S1P1-5), crucial for cardiovascular and immune functions.
• FTY720 (fingolimod) is an S1P receptor modulator approved for multiple sclerosis, acting as a prodrug of FTY720-phosphate.

Purpose of the Study:

• To investigate if cis-4-methylsphingosine (cis-4M-Sph) interacts with S1P receptors, similar to FTY720, via its phosphorylated metabolite, cis-4-methylsphingosine-1-phosphate (cis-4M-S1P).
• To determine the specific S1P receptor subtypes targeted by cis-4M-Sph and its metabolite and their functional consequences.

Main Methods:

• Cells were treated with cis-4M-Sph, and S1P receptor internalization was assessed.
• Calcium mobilization assays ([Ca(2+)](i)) were performed to measure S1P receptor activity.
• Sphingosine kinase (SphK) expression and cis-4M-S1P production were analyzed.

Main Results:

• Cis-4M-Sph induced internalization of S1P receptors, notably S1P2 and S1P3, and weakly S1P1, differing from FTY720's profile.
• Pre-incubation with cis-4M-Sph desensitized S1P-induced calcium increases mediated by S1P2 and S1P3.
• Desensitization was dependent on sphingosine kinase activity (predominantly SphK2) and the formation of cis-4M-S1P.

Conclusions:

• Cis-4M-Sph, through its metabolite cis-4M-S1P, acts as an S1P receptor modulator, inducing receptor internalization and desensitization.
• The distinct receptor targeting profile of cis-4M-Sph, particularly its action on S1P2, differentiates it from FTY720.
• The findings provide crucial information on the requirements for sphingosine kinase substrates to function as effective S1P receptor modulating prodrugs.