Abrogation of apoptosis through PDGF-BB-induced sulfated glycosaminoglycan synthesis and secretion.
Platelet-derived growth factor (PDGF)-BB-stimulated glycosaminoglycan (GAG) synthesis/secretion in fetal lung fibroblasts is dependent on sequential activation of the PDGF beta-receptor, phosphatidylinositol 3-kinase (PI3K), the serine/threonine kinase Akt-1,2, and the GTPase Rab3D. Because the Akt pathway has been implicated in cell survival mechanisms, we investigated whether the pathway regulating GAG synthesis/secretion was antiapoptotic. PDGF-BB treatment protected fetal lung fibroblasts against serum starvation-induced apoptosis, whereas wortmannin, an inhibitor of PI3K, abrogated this protective effect. Transfection of constitutively active Akt into fetal lung fibroblasts also safeguarded the cells from apoptosis induced by serum starvation. To determine whether the antiapoptotic response was due, at least in part, to GAGs, we treated lung fibroblasts with beta-D-xyloside as well as with topically applied GAGs, specifically those produced by fetal lung fibroblasts. beta-D-xyloside increased GAG synthesis/secretion and diminished apoptosis. Application of sulfated GAGs, chondroitin sulfate, and heparan sulfate, but not nonsulfated hyaluronan, also resulted in diminished apoptosis. Moreover, topically applied sulfated GAGs increased Bcl-associated death promoter phosphorylation and diminished caspase-3 and -7 cleavage, indicating an antiapototic response. These data are compatible with the PDGF-BB-GAG signaling pathway regulating programmed fibroblast death in the fetal lung.
Program in Lung Biology, Research Institute, The Hospital for Sick Children, 555 University Ave., Toronto, Ontario, Canada M5G 1X8.
Nicholas J
NJ
Cartel
Martin
M
Post
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D000077214:Becaplermin; D002352:Carrier Proteins / Q000378:metabolism; D053148:Caspase 3; D053179:Caspase 7; D020169:Caspases / Q000737:chemistry / Q000187:drug effects; D002478:Cells, Cultured; D004622:Embryo, Mammalian / Q000166:cytology / Q000378:metabolism; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D006025:Glycosaminoglycans / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism* / Q000494:pharmacology; D006027:Glycosides / Q000494:pharmacology; D008168:Lung / Q000196:embryology*; D008297:Male; D010766:Phosphorylation / Q000187:drug effects; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt; D020574:Proto-Oncogene Proteins c-sis; D051381:Rats; D017208:Rats, Wistar; D012965:Sodium Chloride / Q000494:pharmacology; D051025:bcl-Associated Death Protein
C494821:Bad protein, rat; D002352:Carrier Proteins; D006025:Glycosaminoglycans; D006027:Glycosides; D010982:Platelet-Derived Growth Factor; D011518:Proto-Oncogene Proteins; D020574:Proto-Oncogene Proteins c-sis; D051025:bcl-Associated Death Protein; C010807:xylosides; D000077214:Becaplermin; C013786:A73025; D012965:Sodium Chloride; C494920:Akt1 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; C505410:Casp3 protein, rat; D053148:Caspase 3; D053179:Caspase 7; D020169:Caspases