Constitutively active mitogen-activated protein kinase kinase 6 (MKK6) or salicylate induces spontaneous 3T3-L1 adipogenesis.
Although much has been learned regarding the importance of p38 mitogen-activated protein kinase in inflammatory and stress responses, relatively little is known concerning its role in differentiation processes. Recently, we demonstrated that p38 mitogen-activated protein kinase activity is necessary for the differentiation of 3T3-L1 fibroblasts into adipocytes (Engelman, J. A., Lisanti, M. P., and Scherer, P. E. (1998) J. Biol. Chem. 273, 32111-32120). p38 activity is high during the initial stages of differentiation but decreases drastically as the fibroblasts undergo terminal differentiation into adipocytes. However, it remains unknown whether activation of p38 is sufficient to stimulate adipogenesis and whether the down-regulation of p38 activity in mature adipocytes is critical for maintaining adipocyte homeostasis. In this report, we have directly addressed these questions by analyzing 3T3-L1 cell lines harboring a specific upstream activator of p38 (a constitutively active mitogen-activated protein kinase kinase 6 (MKK6) mutant, MKK6(Glu)) under the control of an inducible promoter. Induction of MKK6(Glu) in 3T3-L1 fibroblasts spurs adipocyte conversion in the absence of the hormonal mixture normally required for efficient differentiation of wild-type cells. However, activation of p38 in adipocytes leads to cell death. Furthermore, treatment of 3T3-L1 fibroblasts with salicylate, a potent stimulator of p38, produces adipocyte-specific changes consistent with those observed with induction of MKK6(Glu). Expression of MKK6(Glu) in NIH-3T3 fibroblasts (cells that do not differentiate into adipocytes under normal conditions) is capable of converting these fibroblasts into lipid-laden fat cells following hormonal stimulation. Thus, p38 activation has pro-adipogenic effects in multiple fibroblast cell lines.
Engelman
J A
JA
Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
Berg
A H
AH
Lewis
R Y
RY
Lin
A
A
Lisanti
M P
MP
Scherer
P E
PE
D016475:3T3 Cells; D017667:Adipocytes / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D019943:Amino Acid Substitution; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D004790:Enzyme Induction; D005347:Fibroblasts; D018698:Glutamic Acid; D007544:Isopropyl Thiogalactoside / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases; D048669:MAP Kinase Kinase 6; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D012980:Sodium Salicylate / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases
D007544:Isopropyl Thiogalactoside; D018698:Glutamic Acid; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048669:MAP Kinase Kinase 6; C482567:Map2k6 protein, mouse; D020929:Mitogen-Activated Protein Kinase Kinases; D012980:Sodium Salicylate