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and -
isoforms
Department of Surgery, The University of Texas Medical Branch, Galveston, Texas 77555-0536
Neurotensin (NT) plays an
important role in gastrointestinal secretion, motility, and growth. The
mechanisms regulating NT secretion are not entirely known. Our purpose
was to define the role of the PKC signaling pathway in secretion of NT
from BON cells, a human pancreatic carcinoid cell line that produces
and secretes NT peptide. We demonstrated expression of all 11 PKC isoforms at varying levels in untreated BON cells. Expression of
PKC-
, -
2, -
, and -µ isoforms was most pronounced.
Immunofluorescent staining showed PKC-
and -µ expression
throughout the cytoplasm and in the membrane. Also, significant
fluorescence of PKC-
was noted in the nucleus and cytoplasm.
Treatment with PMA induced translocation of PKC-
, -
, and -µ
from cytosol to membrane. Activation of PKC-
, -
, and -µ was
further confirmed by kinase assays. Addition of PKC-
inhibitor
Gö-6976 at a nanomolar concentration, other PKC inhibitors
Gö-6983 and GF-109203X, or PKC-
-specific inhibitor rottlerin
significantly inhibited PMA-mediated NT release. Overexpression of
either PKC-
or -
increased PMA-mediated NT secretion compared with control cells. We demonstrated that PMA-mediated NT secretion in
BON cells is associated with translocation and activation of PKC-
,
-
, and -µ. Furthermore, inhibition of PKC-
and -
blocked PMA-stimulated NT secretion, suggesting a critical role for these isoforms in NT release.
protein kinase C; phorbol ester; BON cell line; gut endocrine cells
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