Mechanistic insights into transport models of the sphingolipid transport protein, Spinster homolog 2 (Spns2), using MD simulations

Sphingosine-1-phosphate (S1P) is a sphingolipid signaling molecule that when elevated results in multiple disease states including metastatic cancers. Modulating the extracellular concentrations of S1P has been an evolving strategy in drug development for metastatic cancers due to its role in angiogenesis and cell migration. Research has shown that Spns2, the S1P transport protein, is an important microenvironment regulatory gene in metastatic lung cancer colonization and has demonstrated that Spns2 inhibition is a powerful suppressor of metastatic cancers. Spns2 transports and regulates cellular levels of S1P but has unresolved aspects related to mechanism of transport. Here, molecular modeling strategies including, homology modeling and molecular dynamics (MD) simulations, were used to determine structural mechanisms of action related to S1P transport and exploitable for inhibition. Results indicate Spns2 contains a unique salt-bridge network essential for structural stability that is disrupted by the R119A mutation. Additionally, we observe that Spns2 follows a rocker-switch transport model and that S1P translocation is initialized by interacting with residues such as Thr216, Arg227, and Met230. This work provides initial insight into structural morphologies sampled by Spns2, the role of a complex salt bridge network, and residues engaged in structural state transition that can be targeted with inhibitors to control extracellular concentrations of S1P.