Platelet-derived growth factor-BB and thrombin activate phosphoinositide 3-kinase and protein kinase B: role in mediating airway smooth muscle proliferation.
Proliferation of airway smooth muscle results from persistent inflammatory cytokine and growth factor stimulation and is a critical component of airway luminal narrowing in chronic asthma. Using primary cultures of bovine tracheal smooth muscle (BTSM) cells to examine the signaling basis of cell proliferation, platelet-derived growth factor (PDGF)-BB and thrombin (which act through distinct receptor types) were found to induce DNA synthesis in BTSM cells. Mitogen-induced DNA synthesis could be completely inhibited by LY294002, a selective phosphoinositide 3-kinase (PtdIns 3-kinase) inhibitor. Exposure of BTSM cells to PDGF-BB or thrombin resulted in rapid activation of PtdIns 3-kinase and accumulation of phosphoinositide-3,4,5-trisphosphate. Protein kinase B, a novel signaling protein kinase, was identified in BTSM cells and was activated by PDGF-BB and thrombin in a PtdIns 3-kinase-dependent manner; this may underlie mitogen-stimulated activation of p70(s6k). PD98059, a mitogen-activated protein kinase kinase 1 inhibitor, also partially inhibited PDGF-BB- and thrombin-stimulated DNA synthesis, indicating a modulatory role for mitogen-activated protein kinase in proliferation. GF109203X, Ro 31-8220, calphostin C, and chelerythrine (selective protein kinase C inhibitors) had no effect on PDGF-BB- or thrombin-stimulated DNA synthesis, suggesting that, despite abolishment of mitogen-stimulated protein kinase C activity, cell proliferation stimulated by PDGF-BB and thrombin is protein kinase C-independent. These data demonstrate that the PtdIns 3-kinase/protein kinase B pathway represents a key signaling route in airway smooth muscle proliferation, with the mitogen-activated protein kinase kinase 1/mitogen-activated protein kinase cascade providing a complementary signal required for the full mitogenic response.
Walker
T R
TR
Rayne Laboratory, Respiratory Medicine Unit, Department of Medicine (Royal Infirmary of Edinburgh), University of Edinburgh Medical School, Edinburgh EH8 9AG, UK. trevor.walker@ed.ac.uk
Moore
S M
SM
Lawson
M F
MF
Panettieri
R A
RA
Chilvers
E R
ER
D064413:3-Phosphoinositide-Dependent Protein Kinases; D000818:Animals; D000077214:Becaplermin; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002417:Cattle; D002455:Cell Division / Q000187:drug effects; D004247:DNA / Q000096:biosynthesis; D004789:Enzyme Activation / Q000187:drug effects; D008934:Mitogens / Q000494:pharmacology; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D011493:Protein Kinase C / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D020574:Proto-Oncogene Proteins c-sis; D017479:Receptors, Platelet-Derived Growth Factor / Q000096:biosynthesis; D013917:Thrombin / Q000494:pharmacology*; D013997:Time Factors; D014132:Trachea / Q000187:drug effects* / Q000378:metabolism
D008934:Mitogens; D010982:Platelet-Derived Growth Factor; D011518:Proto-Oncogene Proteins; D020574:Proto-Oncogene Proteins c-sis; D000077214:Becaplermin; D004247:DNA; D017479:Receptors, Platelet-Derived Growth Factor; D064413:3-Phosphoinositide-Dependent Protein Kinases; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D011493:Protein Kinase C; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D013917:Thrombin