title: Upregulation of nuclear factor-kappaB expression by SLURP-1 is mediated by alpha7-nicotinic acetylcholine receptor and involves both ionic events and activation of protein kinases.
abstract: SLURP-1 (secreted mammalian Ly-6/urokinase plasminogen activator receptor-related protein-1) is a novel auto/paracrine cholinergic peptide that can bind to α(7)-nicotinic acetylcholine receptor (nAChR), a high Ca(2+)-permeable ion channel coupled to regulation of nuclear factor-κB (NF-κB) expression. Elucidation of intracellular signaling events elicited by SLURP-1 is crucial for understanding the molecular mechanism of functioning of this novel hormone-like peptide that alters vital cell functions and can protect from tumorigenic transformation. In this study, we sought to dissect out the role of α(7)-nAChR in mediating the biologic effects of recombinant SLURP-1 on the immortalized line of human oral keratinocytes Het-1A. A multifold upregulation of the NF-κB expression at the mRNA and protein levels by SLURP-1 was only slightly diminished due to elimination of Na(+), whereas in Ca(2+)-free medium the effect of SLURP-1 was inhibited by >50%. Both in the absence of extracellular Ca(2+) and in the presence of Cd(2+) or Zn(2+), the SLURP-1-dependent elevation of NF-κB was almost completely blocked by inhibiting MEK1 activity. Downstream of α(7)-nAChR, the SLURP-1 signaling coupled to upregulation of NF-κB also involved Jak2 as well as Ca(2+)/calmodulin-dependent kinase II (CaMKII) and protein kinase C (PKC), whose inhibition significantly (P < 0.05) reduced the SLURP-1-induced upregulation of NF-κB. The obtained results indicated that activation of α(7)-nAChR by SLURP-1 leads to upregulation of the NF-κB gene expression due to activation of the Raf-1/MEK1/ERK1/2 cascade that proceeds via two complementary signaling pathways. One is mediated by the Ca(2+)-entry dependent CaMKII/PKC activation and another one by Ca(2+)-independent involvement of Jak2. Thus, there exists a previously not appreciated network of noncanonical auto/paracrine ligands of nAChR of the Ly-6 protein family, which merits further investigations.
authors.affiliation: Department of Dermatology, University of California, Irvine, California 92697, USA.
authors.forename: Alexander I
authors.initials: AI
authors.lastname: Chernyavsky
authors.forename: Juan
authors.initials: J
authors.lastname: Arredondo
authors.forename: Valentin
authors.initials: V
authors.lastname: Galitovskiy
authors.forename: Jing
authors.initials: J
authors.lastname: Qian
authors.forename: Sergei A
authors.initials: SA
authors.lastname: Grando
mesh_terms: D000818:Animals; D000950:Antigens, Ly / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D004789:Enzyme Activation; D004847:Epithelial Cells / Q000502:physiology*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D053614:Janus Kinase 2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D048369:MAP Kinase Kinase 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D011978:Receptors, Nicotinic / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D015854:Up-Regulation; D014568:Urokinase-Type Plasminogen Activator / Q000235:genetics / Q000378:metabolism*; D064569:alpha7 Nicotinic Acetylcholine Receptor
chemical_list: D000950:Antigens, Ly; C579167:Chrna7 protein, human; D016328:NF-kappa B; D011978:Receptors, Nicotinic; C048963:SLURP1 protein, human; D064569:alpha7 Nicotinic Acetylcholine Receptor; D053614:Janus Kinase 2; D019908:Proto-Oncogene Proteins c-raf; D011493:Protein Kinase C; D048049:Extracellular Signal-Regulated MAP Kinases; D048369:MAP Kinase Kinase 1; D014568:Urokinase-Type Plasminogen Activator