Naslov
De novo ceramide accumulation due to inhibition of its conversion to complex sphingolipids in apoptotic photosensitized cells

Autori
Dolgachev, Vladislav ; Sharjeel Farooqui, M. ; Kulaeva, Olga I. ; Tainsky, Michael A. ; Nagy, Biserka ; Hanada, Kentaro ; Šeparović, Duška

Izvornik
Journal of biological chemistry (0021-9258) 279 (2004), 22; 23238-23249

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
photodynamic therapy; Jurkat human T lymphoma

Sažetak
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 almitoyltransferase (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 alabeling of [14C]ceramide was completely brogated 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 eithermRNAamounts 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.

Izvorni jezik
Engleski

Znanstvena područja
Kliničke medicinske znanosti

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