Possible role of duration of PKC-induced ERK activation in the effects of agonists and phorbol esters on DNA synthesis in panc-1 cells

✍ Scribed by Gábor Z. Rácz; Ákos Szűcs; Vanda Szlávik; János Vág; Beáta Burghardt; Austin C. Elliott; Gábor Varga

• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: English
• Weight: 546 KB
• Volume: 98
• Category: Article
• ISSN: 0730-2312
• DOI: 10.1002/jcb.20913

✦ Synopsis

Abstract

Protein kinase C (PKC) and extracellular signal‐regulated kinase (ERK) have been implicated in the effects of regulatory peptides on proliferation. We studied how ERK was activated by PKC following regulatory peptide or phorbol ester stimulation and we also investigated the effect of ERK activation on proliferation in Panc‐1 cells. Panc‐1 cells transfected with CCK~1~ receptors were treated with cholecystokinin (CCK), neurotensin (NT), or phorbol 12‐myristate 13‐acetate (PMA). DNA synthesis was studied by measuring tritiated thymidine incorporation. PKC isoforms were selectively inhibited with Gö6983 and 200 nM Ro‐32‐0432, their translocation was detected by confocal microscopy and by subcellular fractionation followed by immunoblotting. ERK cascade activation was detected with phosphoERK immunoblotting and inhibited with 20 µM PD98059. PMA and CCK inhibited, NT stimulated DNA synthesis. These effects were inhibited by Ro‐32‐0432 but not by Gö6983 suggesting the involvement of PKCε in proliferation control. Confocal microscopy and subcellular fractionation demonstrated that PMA, CCK, and NT caused cytosol to membrane translocation of PKCε and ERK activation that was inhibited by Ro‐32‐0432 but not by Gö6983. ERK activation was prolonged following PMA and CCK, but transient after NT treatment. PMA, CCK, and NT all activated cyclinD1, while p21CIP1 expression was increased by only PMA and CCK, but not by NT; each of these effects is inhibited by PD98059. In conclusion, our results provide evidence for PKCε‐mediated differential ERK activation and growth regulation in Panc‐1C cells. Identification of the mechanisms by which these key signaling pathways are modulated could provide a basis for the development of novel therapeutic interventions to treat pancreatic cancer. J. Cell. Biochem. © 2006 Wiley‐Liss, Inc.