Mixed lineage kinase 3 inhibits platelet-derived growth factor-stimulated DNA synthesis and matrix mRNA expression in mesangial cells.
Mixed lineage kinase 3 (MLK 3) is a recently described member of the MLK subfamily of Ser/Thr protein kinases that interacts with MAPK pathways. The aim of this study was to test the potential interaction of MLK 3 with signaling pathways stimulated by PDGF in rat mesangial cells. We have established a stable cell line expressing human MLK 3 in rat glomerular mesangial cells. The effects of PDGF on proliferation and matrix mRNA expression were examined. In control (vector-transfected) mesangial cells PDGF increased [(3)H]-thymidine incorporation significantly in a concentration-dependent manner. In mesangial cells expressing MLK 3, PDGF-induced increase in DNA synthesis was significantly reduced. PDGF also induced fibronectin and collagen I mRNA expression in control cells, the effects of which were also significantly blocked in MLK 3-transfected cells. To understand the potential interaction of MLK 3 over expression with the MAPK pathways and to examine the potential mechanism of the effects of MLK 3 over expression on proliferation and matrix expression, activation of ERK2, JNK1 and p38 were examined. ERK2 activation was increased several fold by PDGF in control cells but was attenuated significantly in MLK 3 expressing cells. PDGF did not have any effect on JNK and p38 activation, in either cell types. Using the same stable-transfected cell line, identical results were obtained on proliferation and matrix expression with sarafotoxin-s6b (endothelin receptor agonist) another potent mitogenic and sclerotic agent for mesangial cells. These results indicate an important role for MLK 3 in the regulation of growth and matrix expression in mesangial cells.
Parameswaran
Narayanan
N
Department of Physiology, Michigan State University, East Lansing 48824, USA. paramesw@msu.edu
Hall
Carolyn S
CS
Böck
Barbara C
BC
Sparks
Harvey V
HV
Gallo
Kathleen A
KA
Spielman
William S
WS
D000818:Animals; D000841:Anisomycin / Q000494:pharmacology; D015152:Blotting, Northern; D015153:Blotting, Western; D002478:Cells, Cultured; D003001:Cloning, Molecular; D024042:Collagen Type I / Q000096:biosynthesis / Q000235:genetics; D004247:DNA / Q000096:biosynthesis*; D004789:Enzyme Activation / Q000187:drug effects; D005353:Fibronectins / Q000096:biosynthesis / Q000235:genetics; D005822:Genetic Vectors; D005920:Glomerular Mesangium / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D006801:Humans; D020930:MAP Kinase Kinase Kinases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009154:Mutation; D010982:Platelet-Derived Growth Factor / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis* / Q000235:genetics; D051381:Rats; D014757:Viper Venoms / Q000494:pharmacology; D000097767:Mitogen-Activated Protein Kinase Kinase Kinase 11
D000841:Anisomycin; D024042:Collagen Type I; D004247:DNA; D005353:Fibronectins; D020930:MAP Kinase Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D010982:Platelet-Derived Growth Factor; D012333:RNA, Messenger; D014757:Viper Venoms; D000097767:Mitogen-Activated Protein Kinase Kinase Kinase 11; C057354:sarafotoxins s6