Thymosin beta 4 stimulates laminin-5 production independent of TGF-beta.
Thymosin beta 4 (Tbeta(4)) stimulates epithelial cell migration and promotes laminin-5 (LM-5) expression. Using gene expression analysis with human corneal epithelial cells treated with Tbeta(4), we find that both LM-5 gamma2 chain and transforming growth factor beta 1 (TGFbeta-1) are increased by more than 2-fold over untreated cells. These findings were confirmed by RT-PCR and at the protein level. Although TGFbeta-1 increases LM-5 synthesis in a dose-dependent manner, it does not appear to be the mechanism by which Tbeta(4) acts on LM-5 gamma2 chain synthesis based on three independent experiments. In a time-course analysis, Tbeta(4) increases LM-5 gamma2 chain expression at 2 h and peaks at 6 h, while TGFbeta-1 increases LM-5 gamma2 chain expression only at 4 h and peaks at 8 h. When Tbeta(4)-induced LM-5 gamma2 chain expression is blocked with neutralizing antibodies to TGFbeta-1, LM-5 gamma2 chain expression is increased. Finally, in TGFbeta-1 knock-out mice, Tbeta(4) increases LM-5 gamma2 chain expression to levels higher than that observed in wild-type mice treated with Tbeta(4). These findings demonstrate that Tbeta(4) induces both TGFbeta-1 and LM-5 gamma2 chain expression in corneal epithelial cells. Tbeta(4) and TGFbeta-1 increase LM-5 gamma2 chain expression by independent pathways. Suppression of TGFbeta-1 further increases LM-5 gamma2 chain expression.
Sosne
Gabriel
G
Department of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, MI 48201, USA. gsosne@med.wayne.edu
Xu
Lihua
L
Prach
Lisa
L
Mrock
Linda K
LK
Kleinman
Hynda K
HK
Letterio
John J
JJ
Hazlett
Linda D
LD
Kurpakus-Wheater
Michelle
M
D000818:Animals; D015815:Cell Adhesion Molecules / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D003315:Cornea / Q000166:cytology; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007700:Kinetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D013947:Thymosin / Q000494:pharmacology*; D016212:Transforming Growth Factor beta / Q000378:metabolism* / Q000494:pharmacology; D000097794:Kalinin; D000099201:Thymosin beta(4)
D015815:Cell Adhesion Molecules; D013947:Thymosin; D016212:Transforming Growth Factor beta; D000097794:Kalinin; D000099201:Thymosin beta(4)