Staurosporines decrease ORMDL proteins and enhance sphingomyelin synthesis resulting in depletion of plasmalemmal phosphatidylserine.
Accumulation of phosphatidylserine in the inner leaflet of the plasma membrane is a hallmark of eukaryotes. Sublethal levels of staurosporine and related compounds deplete phosphatidylserine from the plasma membrane and abrogate K-Ras signaling. Here, we report that low-dose staurosporine and related compounds increase sphingomyelin mass. Mass-spectrometry and metabolic tracer analysis revealed an increase in both the levels and rate of synthesis of sphingomyelin in response to sublethal staurosporine. Mechanistically, it was determined that the abundance of the ORMDL proteins, which negatively regulate serine-palmitoyltransferase, are decreased by low-dose staurosporine. Finally, inhibition of ceramide synthesis, and thus sphingomyelin, prevented the displacement of phosphatidylserine and cholesterol from the inner leaflet of the plasma membrane. The results establish that an optimal level of sphingomyelin is required to maintain the distribution of phosphatidylserine and cholesterol in the plasma membrane and further demonstrate a complex relationship between the trafficking of phosphatidylserine and sphingomyelin.
Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, ON, Canada.
Masashi
M
Maekawa
Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, ON, Canada.|Department of Biochemistry, University of Toronto, Toronto, ON, Canada.
Minhyoung
M
Lee
Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, ON, Canada.
Kuiru
K
Wei
Departments of Pediatrics, and Biochemistry &Molecular Biology, Atlantic Research Centre, Dalhousie University, Halifax, Nova Scotia, Canada.
Neale D
ND
Ridgway
Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, ON, Canada.|Department of Biochemistry, University of Toronto, Toronto, ON, Canada.|Department of Surgery, University of Toronto, Toronto, ON, Canada.
Gregory D
GD
Fairn
D000818:Animals; D016466:CHO Cells; D002462:Cell Membrane / Q000378:metabolism; D002518:Ceramides / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D002784:Cholesterol / Q000378:metabolism; D006224:Cricetinae; D003412:Cricetulus; D015536:Down-Regulation / Q000187:drug effects*; D037341:Fumonisins / Q000494:pharmacology; D013058:Mass Spectrometry; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D018613:Microscopy, Confocal; D010718:Phosphatidylserines / Q000172:deficiency / Q000378:metabolism; D013109:Sphingomyelins / Q000032:analysis / Q000096:biosynthesis*; D019311:Staurosporine / Q000494:pharmacology*; D015854:Up-Regulation / Q000187:drug effects*
D002518:Ceramides; D037341:Fumonisins; D008565:Membrane Proteins; D010718:Phosphatidylserines; D013109:Sphingomyelins; C056933:fumonisin B1; D002784:Cholesterol; D019311:Staurosporine