Acute activation of de novo sphingolipid biosynthesis upon heat shock causes an accumulation of ceramide and subsequent dephosphorylation of SR proteins.
Recent studies are beginning to implicate sphingolipids in the heat stress response. In the yeast Saccharomyces cerevisiae, heat stress has been shown to activate de novo biosynthesis of sphingolipids, whereas in mammalian cells the sphingolipid ceramide has been implicated in the heat shock responses. In the current study, we found an increase in the ceramide mass of Molt-4 cells in response to heat shock, corroborating findings in HL-60 cells. Increased ceramide was determined to be from de novo biosynthesis by two major lines of evidence. First, the accumulation of ceramide was dependent upon the activities of both ceramide synthase and serine palmitoyltransferase. Second, pulse labeling studies demonstrated increased production of ceramide through the de novo biosynthetic pathway. Significantly, the de novo sphingolipid biosynthetic pathway was acutely induced upon heat shock, which resulted in a 2-fold increased flux in newly made ceramides within 1-2 min of exposure to 42.5 degrees C. Functionally, heat shock induced the dephosphorylation of the SR proteins, and this effect was demonstrated to be dependent upon the accumulation of de novo-produced ceramides. Thus, these studies disclose an evolutionary conserved activation of the de novo pathway in response to heat shock. Moreover, SR dephosphorylation is emerging as a specific downstream target of accumulation of newly made ceramides in mammalian cells.
Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina 29425, USA.
Gary M
GM
Jenkins
L Ashley
LA
Cowart
Paola
P
Signorelli
Benjamin J
BJ
Pettus
Charles E
CE
Chalfant
Yusuf A
YA
Hannun
D001692:Biological Transport / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002518:Ceramides / Q000378:metabolism*; D005229:Fatty Acids, Monounsaturated / Q000493:pharmacokinetics; D037341:Fumonisins / Q000494:pharmacology; D018922:HL-60 Cells; D006358:Hot Temperature; D006801:Humans; D007700:Kinetics; D008861:Microsomes / Q000378:metabolism; D009183:Mycotoxins / Q000494:pharmacology; D009687:Nuclear Proteins / Q000378:metabolism*; D019308:Palmitic Acid / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism*; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma; D016601:RNA-Binding Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D000068103:Serine-Arginine Splicing Factors; D013107:Sphingolipids / Q000096:biosynthesis*; D014407:Tumor Cells, Cultured
D002518:Ceramides; D005229:Fatty Acids, Monounsaturated; D037341:Fumonisins; D009183:Mycotoxins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D016601:RNA-Binding Proteins; D013107:Sphingolipids; D000068103:Serine-Arginine Splicing Factors; D019308:Palmitic Acid; C056933:fumonisin B1; C001996:thermozymocidin