Native and polyubiquitinated forms of dihydroceramide desaturase are differentially linked to human embryonic kidney cell survival

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Alsanafi, Mariam and Kelly, Samuel L. and Jubair, Karawan and McNaughton, Melissa and Tate, Rothwelle J. and Merrill Jr., Alfred H. and Pyne, Susan and Pyne, Nigel J. (2018) Native and polyubiquitinated forms of dihydroceramide desaturase are differentially linked to human embryonic kidney cell survival. Molecular and Cellular Biology, 38. e00222. ISSN 0270-7306 (https://doi.org/10.1128/MCB.00222-18)

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Abstract

There is controversy concerning the role of dihydroceramide desaturase (Degs1) in regulating cell survival with studies showing that it can both promote and protect against apoptosis. We have therefore, investigated the molecular basis for these opposing roles of Degs1. Treatment of HEK293T cells with the sphingosine kinase inhibitor, SKi (2-(p-hydroxyanilino)-4-(p-chlorophenyl)thiazole)) or fenretinide, but not the Degs1 inhibitor, GT11 (((N-[(1R,2S)-2-hydroxy-1-hydroxymethyl-2-(2-tridecyl-1-cyclopropenyl)ethyl]octan-amide)) induced the polyubiquitination of Degs1 (Mr=40-140 kDa) via a mechanism involving oxidative stress, p38 MAPK and Mdm2 (E3 ligase). The polyubiquitinated forms of Degs1 exhibit ‘gain of function’ and activate pro-survival pathways, p38 MAPK, JNK and X-box protein-1s (XBP-1s). In contrast, another sphingosine kinase inhibitor, ABC294640 (3-(4-chlorophenyl)-adamantane-1-carboxylic acid (pyridin-4-ylmethyl)amide) at concentrations of 25-50 uM failed to induce formation of the polyubiquitinated forms of Degs1. In contrast with SKi, ABC294640 (25 uM) promotes apoptosis of HEK293T cells via a Degs1-dependent mechanism that is associated with increased de novo synthesis of ceramide. These findings are the first to demonstrate that the polyubiquitination of Degs1 appears to change its function from pro-apoptotic to pro-survival. Thus, polyubiquitination of Degs1 might provide an explanation for the reported opposing functions of this enzyme on cell survival/apoptosis.

ORCID iDs

Alsanafi, Mariam ORCID logoORCID: https://orcid.org/0000-0001-9977-2462, Kelly, Samuel L., Jubair, Karawan, McNaughton, Melissa ORCID logoORCID: https://orcid.org/0000-0001-5080-6043, Tate, Rothwelle J., Merrill Jr., Alfred H., Pyne, Susan ORCID logoORCID: https://orcid.org/0000-0002-6608-9584 and Pyne, Nigel J. ORCID logoORCID: https://orcid.org/0000-0002-5657-4578;
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