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Molecular cloning and characterization of a Drosophila p38 mitogen-activated protein kinase
1Laboratory of Immunology, Medical Research Center, College of Medicine, Yonsei University, CPO Box 8044, Seoul, South Korea.
Abstract:
A mitogen-activated protein kinase (MAPK) has been cloned and sequenced from a Drosophila neoplasmic l(2)mbn cell line. The cDNA sequence analysis showed that this Drosophila kinase is a homologue of mammalian p38 MAPK and the yeast HOG1 gene and thus was referred to as Dp38. A distinguishing feature of all MAPKs is the conserved sequence TGY in the activation domain. Dp38 was rapidly tyrosine 186-phosphorylated in response to osmotic stress, heat shock, serum starvation, and H2O2 in Drosophila l(2)mbn and Schneider cell lines. However, unlike mammalian p38 MAPK, the addition of lipopolysaccharide (LPS) did not significantly affect the phosphorylation of Dp38 in the LPS-responsive l(2)mbn cell line. Following osmotic stress, tyrosine 186-phosphorylated forms of Dp38 MAPK were detected exclusively in nuclear regions of Schneider cells. Yeast complementation studies demonstrated that the Saccharomyces cerevisiae HOG1 mutant strain JBY10 (hog1-Delta1) was functionally complemented by Dp38 cDNA in hyperosmolar medium. These findings demonstrate that similar osmotic stress-responsive signal transduction pathways are conserved in yeast, Drosophila, and mammalian cells, whereas LPS signal transduction pathways appear to be different.
Insights
A newly identified Drosophila mitogen-activated protein kinase (MAPK), Dp38, responds to osmotic stress, similar to yeast and mammalian cells. However, Dp38 does not show a significant response to lipopolysaccharide (LPS).
Area of Science:
- Molecular Biology
- Cell Signaling
- Genetics
Background:
- Mitogen-activated protein kinases (MAPKs) are crucial signaling proteins involved in cellular responses.
- The p38 MAPK pathway and the yeast HOG1 pathway regulate responses to environmental stress.
- Understanding conserved signaling pathways across species provides insights into fundamental biological processes.
Purpose of the Study:
- To clone and characterize a novel MAPK from Drosophila melanogaster.
- To investigate the functional role and activation mechanisms of the Drosophila MAPK homolog (Dp38).
- To compare the stress-response pathways of Dp38 with its mammalian and yeast counterparts.
Main Methods:
- cDNA cloning and sequencing of a Drosophila MAPK.
- Phosphorylation analysis of Dp38 in response to various stimuli (osmotic stress, heat shock, H2O2, LPS).
- Subcellular localization studies of phosphorylated Dp38.
- Functional complementation assays in a Saccharomyces cerevisiae hog1 mutant strain.
Main Results:
- A Drosophila MAPK, Dp38, was identified as a homolog of mammalian p38 MAPK and yeast HOG1.
- Dp38 undergoes tyrosine 186-phosphorylation in response to osmotic stress, heat shock, serum starvation, and H2O2.
- Unlike mammalian p38 MAPK, Dp38 phosphorylation was not significantly induced by lipopolysaccharide (LPS).
- Phosphorylated Dp38 localized to the nucleus following osmotic stress.
- Dp38 functionally complemented a yeast hog1 mutant under hyperosmolar conditions.
Conclusions:
- Conserved osmotic stress-responsive signaling pathways exist between yeast, Drosophila, and mammals.
- The regulation of Dp38 by LPS differs from mammalian p38 MAPK, suggesting species-specific adaptations in signaling.
- Dp38 serves as a valuable model for studying conserved stress-response mechanisms in eukaryotes.