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The American Journal of Physiology - Cell Physiology
Year: 2010 | Volume: 299 | Issue: 5 | Page No.: 903 - 911
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Upregulation of nuclear factor-{kappa}B expression by SLURP-1 is mediated by {alpha}7-nicotinic acetylcholine receptor and involves both ionic events and activation of protein kinases
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A. I Chernyavsky,
J Arredondo,
V Galitovskiy,
J Qian
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S. A. Grando
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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 7-nicotinic acetylcholine receptor (nAChR), a high Ca2+-permeable ion channel coupled to regulation of nuclear factor-B (NF-B) 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 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-B expression at the mRNA and protein levels by SLURP-1 was only slightly diminished due to elimination of Na+, whereas in Ca2+-free medium the effect of SLURP-1 was inhibited by >50%. Both in the absence of extracellular Ca2+ and in the presence of Cd2+ or Zn2+, the SLURP-1-dependent elevation of NF-B was almost completely blocked by inhibiting MEK1 activity. Downstream of 7-nAChR, the SLURP-1 signaling coupled to upregulation of NF-B also involved Jak2 as well as Ca2+/calmodulin-dependent kinase II (CaMKII) and protein kinase C (PKC), whose inhibition significantly (P < 0.05) reduced the SLURP-1-induced upregulation of NF-B. The obtained results indicated that activation of 7-nAChR by SLURP-1 leads to upregulation of the NF-B 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 Ca2+-entry dependent CaMKII/PKC activation and another one by Ca2+-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. |
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