title: The expression and role of non-canonical (PKC) signaling in nucleus pulposus cell metabolism.
abstract: Canonical Wnt/β-catenin (hereafter Wnt) signaling regulates the proliferation and differentiation of various cell types. However, the role of non-canonical signaling including protein kinase C (PKC) signaling has not been investigated in intervertebral disc (IVD) cells. The aim of this study was to elucidate whether the activation of PKC signaling act to modulate Wnt signaling in IVD cells. We performed several reporter assays, real-time reverse transcription polymerase chain reaction (RT-PCR), immunohistochemical and immunofluorescence analyses, and western blot analyses using rat nucleus pulposus (NP) cells. We also examined the cell proliferation and cell cycle distribution under phorbol 12-myristate 13-acetate (PMA) stimulation, a known activator of PKC signaling. We found that NP cells exhibited decreased β-catenin mRNA and protein levels upon stimulation with PMA. PMA treatment promoted proliferation and cell cycle progression in a time- and dose-dependent manner. In addition, activation of the PKC signaling also regulated the expression of aggrecan. Finally, activation by PMA induced the expression of several PKC isoforms in NP cells. It is concluded that activation of PKC signaling might lead to an increase in matrix synthesis and cell proliferation, thereby inhibiting IVD degeneration. Crosstalk in these signaling pathways plays an important role in the regulation of IVD homeostasis.
authors.affiliation: Department of Orthopaedic Surgery, Surgical Science, Tokai University School of Medicine, 143 Shimokasuya, Isehara, Kanagawa 259-1193, Japan.
authors.forename: Fumiyuki
authors.initials: F
authors.lastname: Arai
authors.forename: Akihiko
authors.initials: A
authors.lastname: Hiyama
authors.forename: Daisuke
authors.initials: D
authors.lastname: Sakai
authors.forename: Katsuya
authors.initials: K
authors.lastname: Yokoyama
authors.forename: Joji
authors.initials: J
authors.lastname: Mochida
mesh_terms: D053674:Aggrecans / Q000378:metabolism; D000818:Animals; D006025:Glycosaminoglycans / Q000378:metabolism; D007403:Intervertebral Disc / Q000201:enzymology*; D007527:Isoenzymes / Q000378:metabolism; D010703:Phorbol Esters; D011493:Protein Kinase C / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D051153:Wnt Proteins / Q000378:metabolism*
chemical_list: D053674:Aggrecans; D006025:Glycosaminoglycans; D007527:Isoenzymes; D010703:Phorbol Esters; D012333:RNA, Messenger; D051153:Wnt Proteins; C119222:phorbol-12-myristate; D011493:Protein Kinase C