LASP1, CERS6, and Actin Form a Ternary Complex That Promotes Cancer Cell Migration

SIMPLE SUMMARY: CERS6 is known to be associated with metastasis and poor prognosis in non-small cell lung cancer (NSCLC) patients because of C16 ceramide production, though the underlying mechanism remains largely unelucidated. In this study, CERS6 binding partners were identified by co-immunoprecipitation, as well as liquid chromatography and tandem mass spectrometry analysis. LASP1, one of the leading candidates, was found to play a role in cell migration, while CERS6 and LASP1 were shown to co-localize on lamellipodia and interact with actin. Silencing of CERS6 and/or LASP1 led to reduced levels of lamellipodia formation and cell migration. Furthermore, interaction of CERS6 or LASP1 with actin was dramatically decreased when the partner was depleted. Based on these findings, it is proposed that LASP1–CERS6 interaction promotes cancer cell migration. ABSTRACT: CERS6 is associated with metastasis and poor prognosis in non-small cell lung cancer (NSCLC) patients through d18:1/C16:0 ceramide (C16 ceramide)-mediated cell migration, though the detailed mechanism has not been elucidated. In the present study, examinations including co-immunoprecipitation, liquid chromatography, and tandem mass spectrometry analysis were performed to identify a novel binding partner of CERS6. Among the examined candidates, LASP1 was a top-ranked binding partner, with the LIM domain possibly required for direct interaction. In accord with those findings, CERS6 and LASP1 were found to co-localize on lamellipodia in several lung cancer cell lines. Furthermore, silencing of CERS6 and/or LASP1 significantly suppressed cell migration and lamellipodia formation, whereas ectopic addition of C16 ceramide partially rescued those phenotypes. Both LASP1 and CERS6 showed co-immunoprecipitation with actin, with those interactions markedly reduced when the LASP1–CERS6 complex was abolished. Based on these findings, it is proposed that LASP1–CERS6 interaction promotes cancer cell migration.