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Articles in PresS, published online ahead of print August 14, 2002
Am J Physiol Gastrointest Liver Physiol, 10.1152/ajpgi.00177.2002
Submitted on May 13, 2002
Accepted on August 1, 2002
AND
ISOFORMS
1 Department of Surgery, The University of Texas Medical Branch, Galveston, Texas, USA
* To whom correspondence should be addressed. E-mail: mevers{at}utmb.edu.
Neurotensin (NT), a gut tridecapeptide, plays an important role in gastrointestinal (GI) secretion, motility and growth; the mechanisms regulating NT secretion are not entirely known. The purpose of our present study was to define the role of the protein kinase C (PKC) signaling pathway in the secretion of NT from BON® cells, a human pancreatic carcinoid cell line that produces and secretes NT peptide. Here, we demonstrate expression of all 11 PKC isoforms at varying levels in untreated BON® cells; the expression of the PKC
, ß2,
and µ isoforms was most pronounced. Immunofluorescent staining showed PKC
and µ expression throughout the cytoplasm and in the membrane. In addition, significant fluorescence of PKC
was noted in the nucleus and the cytoplasm. Treatment with phorbol 12-myristate 13-acetate (PMA) induced translocation of PKC
,
and µ from the cytosol to the membrane. Activation of PKC
,
and µ was further confirmed by kinase assays. Addition of the PKC
inhibitor, Go6976 at nanomolar concentration, and other PKC inhibitors, Go6983 and GF109203X, or the PKC
-specific inhibitor, Rottlerin, significantly inhibited PMA-mediated NT release. Moreover, overexpression of either PKC
or PKC
increased PMA-mediated NT secretion compared with control cells. In conclusion, we demonstrate that PMA-mediated NT secretion in the endocrine cell line BON® is associated with translocation and activation of the PKC isoforms
,
and µ. Furthermore, inhibition of PKC
and
blocked PMA-stimulated NT secretion, suggesting a critical role for these isoforms in NT release.
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