Metabolism of HSAN1- and T2DM-associated 1-deoxy-sphingolipids inhibits the migration of fibroblasts

J Lipid Res. 2021 Sep 23;62:100122. doi: 10.1016/j.jlr.2021.100122. Online ahead of print.

Abstract

Hereditary sensory neuropathy type 1 (HSAN1) is a rare axonopathy, characterized by a progressive loss of sensation (pain, temperature, and vibration), neuropathic pain and wound healing defects. HSAN1 is caused by several missense mutations in the SPTLC1 and SPTLC2 subunit of the enzyme serine-palmitoyltransferase (SPT) -the key enzyme for the synthesis of sphingolipids. The mutations change the substrate specificity of SPT, which then forms an atypical class of 1-deoxy-sphinglipids (1-deoxySL). Similarly, patients with type 2 diabetes (T2DM) also present with elevated 1-deoxySLs and a comparable clinical phenotype. The effect of 1-deoxySLs on neuronal cells was investigated in detail, but their impact on other cell types remains elusive. Here we investigated the consequences of externally added 1-deoxySLs on the migration of fibroblasts in a scratch assay as a simplified cellular wound-healing model. We showed that 1-deoxy-Sphinganine (1-deoxySA) inhibits the migration of NIH-3T3 fibroblasts in a dose- and time-dependent manner. This was not seen for a non-native, L-threo stereoisomer. Supplemented 1-deoxySA was metabolized to 1-deoxy-(dihydro)Ceramide and downstream to 1-deoxy-Sphingosine (1-deoxySO). Inhibiting downstream metabolism by blocking N-acylation rescued the migration phenotype. In contrast, adding 1-deoxySO had a lesser effect on cell migration but caused the massive formation of intracellular vacuoles. Further experiments showed, that the effect on cell migration was primarily mediated by 1-deoxy-dihydroceramides rather than by the free base or 1-deoxyceramides. Based on these findings, we suggest that limiting the N-acylation of 1-deoxySA could be a therapeutic approach to improve cell migration and wound healing in patients with HSAN1 and T2DM.

Keywords: 1-deoxySphingolipids; Fumonisin B1; Sphingolipid; T2DM; cell migration; ceramide; ceramide synthase; functional lipidomics; live cell imaging; metabolism.