title: Protein kinase C-delta transactivates platelet-derived growth factor receptor-alpha in mechanical strain-induced collagenase 3 (matrix metalloproteinase-13) expression by osteoblast-like cells.
abstract: Matrix metalloproteinase-13 (MMP-13, or collagenase 3) has been shown to degrade intact collagen and to participate in situations where rapid and effective remodeling of collagenous ECM is required. Mechanical strain induction of MMP-13 is an example of how osteoblasts respond to high mechanical forces and participate in the bone-remodeling mechanism. Using MC3T3-E1 osteoblast-like cells, we dissected the signaling molecules involved in MMP-13 induction by mechanical strain. Reverse transcription-PCR and zymogram analysis showed that platelet-derived growth factor receptor (PDGFR) inhibitor, AG1296, inhibited the mechanical strain-induced MMP-13 gene and activity. However, the induction was not affected by anti-PDGF-AA serum. Immunoblot analysis revealed time-dependent phosphorylation of PDGFR-alpha up to 2.7-fold increases within 3 min under strain. Transfection with shPDGFR-alpha (at 4 and 8 microg/ml) abolished PDGFR-alpha and reduced MMP-13 expression. Moreover, time-dependent recruitments of phosphoinositide 3-kinase (PI3K) by PDGFR-alpha were detected by immunoprecipitation with anti-PDGFR-alpha serum followed by immunoblot with anti-PI3K serum. AG1296 inhibited PDGFR-alpha/PI3K aggregation and Akt phosphorylation. Interestingly, protein kinase C-delta (PKC-delta) inhibitor, rottlerin, inhibited not only PDGFR-alpha/PI3K aggregation but PDGFR-alpha phosphorylation. The sequential activations were further confirmed by mutants DeltaPKC-delta, DeltaAkt, and DeltaERK1. Consistently, the primary mouse osteoblast cells used the same identified signaling molecules to express MMP-13 under mechanical strain. These results demonstrate that, in osteoblast-like cells, the MMP-13 induction by mechanical strain requires the transactivation of PDGFR-alpha by PKC-delta and the cross-talk between PDGFR-alpha/PI3K/Akt and MEK/ERK pathways.
authors.affiliation: Department of Pharmacology, Chang Gung University, Tao-Yuan 333, Taiwan.
authors.forename: Chuen-Mao
authors.initials: CM
authors.lastname: Yang
authors.forename: Hsi-Lung
authors.initials: HL
authors.lastname: Hsieh
authors.forename: Chung-Chen
authors.initials: CC
authors.lastname: Yao
authors.forename: Li-Der
authors.initials: LD
authors.lastname: Hsiao
authors.forename: Chin-Ping
authors.initials: CP
authors.lastname: Tseng
authors.forename: Chou Bing
authors.initials: CB
authors.lastname: Wu
mesh_terms: D000818:Animals; D016723:Bone Remodeling / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000502:physiology*; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D053509:Matrix Metalloproteinase 13 / Q000096:biosynthesis* / Q000235:genetics; D040542:Mechanotransduction, Cellular / Q000187:drug effects / Q000502:physiology; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D010006:Osteoblasts; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D051745:Protein Kinase C-delta / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D020796:Receptor, Platelet-Derived Growth Factor alpha / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors; D015533:Transcriptional Activation / Q000187:drug effects / Q000502:physiology*; D020032:Tyrphostins / Q000494:pharmacology
chemical_list: D020032:Tyrphostins; C106250:6,7-dimethoxy-3-phenylquinoxaline; D019869:Phosphatidylinositol 3-Kinases; D020796:Receptor, Platelet-Derived Growth Factor alpha; D051057:Proto-Oncogene Proteins c-akt; D051745:Protein Kinase C-delta; D020929:Mitogen-Activated Protein Kinase Kinases; D053509:Matrix Metalloproteinase 13; C507081:Mmp13 protein, mouse