Chorein addiction in VPS13A overexpressing rhabdomyosarcoma cells

// Sabina Honisch 1 , Willi Yu 1 , Guilai Liu 1 , Ioana Alesutan 1 , Syeda T. Towhid 1 , Anna Tsapara 2 , Sabine Schleicher 3 , Rupert Handgretinger 3 , Christos Stournaras 1,2,* and Florian Lang 1,* 1 Department of Physiology, University of Tubingen, Tubingen, Germany 2 Department of Biochemistry, University of Crete Medical School, Heraklion, Greece 3 Department of Hematology and Oncology, Children’s Hospital, University Hospital of Tuebingen, Tubingen, Germany * These authors are contributed equally and thus share last authorship Correspondence to: Florian Lang, email: // Keywords : cancer, apoptosis, PI-3K, BCL-2, bax Received : July 31, 2014 Accepted : February 13, 2015 Published : March 14, 2015 Abstract Chorein encoded by VPS13A (vacuolar protein sorting-associated protein 13A) is defective in chorea-acanthocytosis. Chorein fosters neuronal cell survival, cortical actin polymerization and cell stiffness. In view of its anti-apoptotic effect in neurons, we explored whether chorein is expressed in cancer cells and influences cancer cell survival. RT-PCR was employed to determine transcript levels, specific siRNA to silence chorein, FACS analysis to follow apoptosis and Western blotting to quantify protein abundance. Chorein transcripts were detected in various cancer cell types. The mRNA coding for chorein and chorein protein were most abundant in drug resistant, poorly differentiated human rhabdomyosarcoma cells. Chorein silencing significantly reduced the ratio of phosphorylated (and thus activated) to total phosphoinositide 3 kinase (PI-3K), pointing to inactivation of this crucial pro-survival signaling molecule. Moreover, chorein silencing diminished transcript levels and protein expression of anti-apoptotic BCL-2 and enhanced transcript levels of pro-apoptotic Bax. Silencing of chorein in rhabdomyosarcoma cells was followed by mitochondrial depolarization, caspase 3 activation and stimulation of early and late apoptosis. In conclusion, chorein is expressed in various cancer cells. In cells with high chorein expression levels chorein silencing promotes apoptotic cell death, an effect paralleled by down-regulation of PI-3K activity and BCL-2/Bax expression ratio.