De Novo Ceramide Accumulation Due to Inhibition of Its Conversion to Complex Sphingolipids in Apoptotic Photosensitized Cells*

By Vladislav A. Dolgachev, M. Sharjeel Farooqui, O. Kulaeva, M. Tainsky, B. Nagy, K. Hanada, D. Separovic. 2004

62 citations recorded by the source corpus.

The oxidative stress induced by photodynamic therapy (PDT) with the photosensitizer phthalocyanine 4 is accompanied by increases in ceramide mass. To assess the regulation of de novo sphingolipid metabolism during PDT-induced apoptosis, Jurkat human T lymphoma and Chinese hamster ovary cells were labeled with [14C]serine, a substrate of serine palmitoyltransferase (SPT), the enzyme catalyzing the initial step in the sphingolipid biosynthesis. A substantial elevation in [14C]ceramide with a concomitant decrease in [14C]sphingomyelin was detected. The labeling of [14C]ceramide was completely abrogated by the SPT inhibitor ISP-1. In addition, ISP-1 partly suppressed PDT-induced apoptosis. Pulse-chase experiments showed that the contribution of sphingomyelin degradation to PDT-initiated increase in de novo ceramide was absent or minor. PDT had no effect on either mRNA amounts of the SPT subunits LCB1 and LCB2, LCB1 protein expression, or SPT activity in Jurkat cells. Moreover in Chinese hamster ovary cells LCB1 protein underwent substantial photodestruction, and SPT activity was profoundly inhibited after treatment. We next examined whether PDT affects conversion of ceramide to complex sphingolipids. Sphingomyelin synthase, as well as glucosylceramide synthase, was inactivated by PDT in both cell lines in a dose-dependent manner. These results are the first to show that in the absence of SPT up-regulation PDT induces accumulation of de novo ceramide by inhibiting its conversion to complex sphingolipids.

Subfields: Materials Chemistry, Molecular Biology, Pulmonary and Respiratory Medicine

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Molecular Biology

Citations in the corpus

Mammalian Ceramide Synthases (2010, background): “1) in the endoplasmic reticulum (ER) by a pathway that begins with the condensation of L-serine and palmitoyl CoA by serine palmitoyl transferase (4) generating 3-ketosphinganine, which is then reduced to sphinganine via 3-ketosphinganine reductase (5).”
Roles of bioactive sphingolipids in cancer biology and therapeutics. (2008, background): “In addition to the activation of sphingomyelinases (SMases) (Andrieu-Abadie and Levade, 2002; Clarke and Hannun, 2006; Clarke et al., 2006) that hydrolyze SM to yield ceramide, endogenous ceramide can be generated via the de novo pathway (Dolgachev et al., 2004; Reynolds et al., 2004).”