Activation of Nuclear Factor {kappa}B by Somatostatin Type 2 Receptor in Pancreatic Acinar AR42J Cells Involves G{alpha}14 and Multiple Signaling Components: A MECHANISM REQUIRING PROTEIN KINASE C, CALMODULIN-DEPENDENT KINASE II, ERK, AND c-Src

doi:10.1074/jbc.M504264200

Ideal method for primary cell transfection

Activation of Nuclear Factor ${kappa}$ B by Somatostatin Type 2 Receptor in Pancreatic Acinar AR42J Cells Involves G ${alpha}$ ₁₄ and Multiple Signaling Components

A MECHANISM REQUIRING PROTEIN KINASE C, CALMODULIN-DEPENDENT KINASE II, ERK, AND c-Src^*

Andrew M. F. Liu and Yung H. Wong1

From the Department of Biochemistry, Molecular Neuroscience Center, and Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China

Medications targeting the somatostatin type 2 receptor (SSTR2)have been employed for pancreatic inflammations and cancers,possibly via the regulation of the transcription factor nuclearfactor ${kappa}$ B (NF ${kappa}$ B). Here we demonstrate that in tumoral pancreaticacinar AR42J cells, activation of SSTR2 leads to stimulationof the inhibitor ${kappa}$ B kinase (IKK)/NF ${kappa}$ B signaling cascade via pertussistoxin-insensitive G proteins in a time- and dose-dependent manner.The inability of G_q/11 and G_12/13 proteins to activate IKK/NF ${kappa}$ Bby SSTR2 in transfected human embryonic kidney 293 cells andthe lack of G ${alpha}$ ₁₆ in AR42J cells suggested a possible role ofG ${alpha}$ ₁₄ in mediating SSTR2-induced responses. This regulatory roleof G ${alpha}$ ₁₄ was further confirmed by the activation of IKK and NF ${kappa}$ Bin human embryonic kidney 293 cells expressing SSTR2 and G ${alpha}$ ₁₄upon induction. The stimulatory effect of G ${beta}$ ₁ ${gamma}$ ₂ and the abrogationby overexpressing transducin confirmed the participation ofG ${beta}$ ${gamma}$ in SSTR2-mediated IKK/NF ${kappa}$ B activation. By the application ofspecific inhibitors and dominant negative mutants, phospholipaseC ${beta}$ , protein kinase C, and calmodulin-dependent kinase II wereshown to be involved in SSTR2-induced responses. Inhibitionof c-Src and numerous intermediates, including Ras, Raf-1 kinase,MEK1/2, along with the extracellular signal-regulated kinasecascade attenuated somatostatin-mediated IKK/NF ${kappa}$ B activation.Although c-Jun N-terminal kinase and p38 mitogen-activated proteinkinase (MAPK) were also stimulated by SSTR2, suppression ofthese two MAPKs was ineffective in altering the somatostatin-mediatedresponses. Similar results were also obtained using AR42J cells.These data suggest that activation of the IKK/NF ${kappa}$ B signalingcascade by SSTR2 requires a complicated network consisting ofG ${alpha}$ ₁₄ and multiple intermediates.

Received for publication, April 19, 2005 , and in revised form, August 18, 2005.

^* This work was supported in part by Research Grants Council ofHong Kong Grants HKUST 6120/04M and HKUST 3/03C, the UniversityGrants Committee Grant AoE/B-15/01, and the Hong Kong JockeyClub. The costs of publication of this article were defrayedin part by the payment of page charges. This article must thereforebe hereby marked "advertisement" in accordance with 18 U.S.C.Section 1734 solely to indicate this fact.

¹ To whom correspondence should be addressed. Tel.: 852-2358-7328; Fax: 852-2358-1552; E-mail: boyung{at}ust.hk.

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