Endoglin modulation of TGF-beta1-induced collagen synthesis is dependent on ERK1/2 MAPK activation.
OBJECTIVE
Transforming growth factor-beta1 (TGF-beta1) plays a pivotal role in the extracellular matrix accumulation observed in fibrotic diseases. Endoglin is an important component of the TGF-beta receptor complex highly expressed in tissues undergoing fibrotic processes. Endoglin expression regulates the effect of TGF-beta on extracellular matrix synthesis. The purpose of our study has been to understand the molecular mechanism by which endoglin exerts its effects on fibrosis and the possible role of MAP kinases in these effects.


METHODS
We have assessed in mock and in endoglin-transfected L6E9 myoblasts the effect of TGF-beta1 on collagen mRNA by Northern blot and effect of TGF-beta1 on collagen content in the cultured medium by [(3)H]-Proline incorporation into collagen proteins. Total and activated MAPK and their role on collagen synthesis were assessed by Western blot.


RESULTS
TGF-beta1 induced an increase on alpha(2) (I) collagen mRNA expression and collagen accumulation in mock-transfected myoblasts, whereas the response was much lower in endoglintransfected cells. TGF-beta1 activated the ERK1/2 and p38 MAPK pathways but not the JNK pathway in L6E9 myoblasts. TGF-beta1-induced alpha(2) (I) collagen mRNA expression and collagen accumulation were completely inhibited by SB203580, in either mock or endoglintransfected myoblasts. PD98059 increased TGF-beta1 induced-collagen synthesis and accumulation in endoglin-transfected myoblasts but not in mock cells.


CONCLUSIONS
Our studies demonstrate that TGF-beta1- induced collagen synthesis is mediated by p38 MAPK activation in L6E9 myoblasts. Furthermore, endoglin expression reduces basal and TGF-beta1 induced collagen synthesis when ERK1/2 pathway is operating.
Rodríguez-Barbero
Alicia
A
Instituto "Reina Sofía" de Investigación Nefrológica, Departamento de Fisiología & Farmacología, Campus Miguel de Unamuno, Avda. Campo Charro s/n, 37007 Salamanca, Spain.
Obreo
Juana
J
Alvarez-Munoz
Patricia
P
Pandiella
Atanasio
A
Bernabéu
Carmelo
C
López-Novoa
José M
JM
D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000502:physiology*; D015152:Blotting, Northern; D015153:Blotting, Western; D002460:Cell Line; D003094:Collagen / Q000235:genetics* / Q000378:metabolism; D000071063:Endoglin; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011956:Receptors, Cell Surface / Q000235:genetics / Q000502:physiology*; D013997:Time Factors; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D053773:Transforming Growth Factor beta1
D015703:Antigens, CD; C064206:ENG protein, human; D000071063:Endoglin; D004791:Enzyme Inhibitors; D005419:Flavonoids; D007093:Imidazoles; D011725:Pyridines; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; C508960:TGFB1 protein, human; C508962:Tgfb1 protein, rat; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D003094:Collagen; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases; C093642:SB 203580; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one