Regulation of the actin cytoskeleton by p125 focal adhesion kinase in rat pancreatic acinar cells.
OBJECTIVE
Activation of p125 focal adhesion kinase by cholecystokinin (CCK)-8 has recently been demonstrated in pancreatic acinar cells. The purpose of this study is to examine downstream events of this kinase.


METHODS
Activation of p125 focal adhesion kinase in freshly isolated rat pancreatic acinar cells was determined by Western blot analysis. Actin cytoskeletal changes were visualized on TRITC-phalloidin-stained cryosections. Amylase release was measured by colorimetric assay.


RESULTS
CCK-8 caused dose-dependent activation of p125 focal adhesion kinase. Time-course analysis showed rapid activation with maximum between 5 and 10 min and stimulation still detectable after 60 min. Preincubation with 2 microM cytochalasin D specifically inhibited p125 focal adhesion kinase, but not p42 mitogen-activated protein kinase or increases in intracellular calcium concentrations. The actin cytoskeleton showed rapid reorganization after stimulation, with an initial increase in fluorescence followed by a decline after 30 min. Preincubation with cytochalasin D prevented cytoskeletal changes. Amylase release at concentrations up to 0.1 nM CCK-8 was not influenced by cytochalasin D. In contrast, supramaximal inhibition of amylase release was less pronounced after cytochalasin D incubation.


CONCLUSIONS
p125 focal adhesion kinase in acinar cells appears to be part of a signalling pathway leading to changes in cellular morphology via the actin cytoskeleton. Maximal activation of this signalling pathway might participate in supramaximal inhibition of enzyme secretion.
Kiehne
K
K
First Department of Internal Medicine, Christian-Albrechts Universität Kiel, Germany.
Herzig
K H
KH
Fölsch
U R
UR
D000199:Actins / Q000378:metabolism*; D000818:Animals; D015815:Cell Adhesion Molecules / Q000187:drug effects / Q000378:metabolism*; D002766:Cholecystokinin / Q000494:pharmacology; D015638:Cytochalasin D / Q000494:pharmacology; D003599:Cytoskeleton / Q000201:enzymology*; D004789:Enzyme Activation / Q000187:drug effects; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D010179:Pancreas / Q000201:enzymology* / Q000648:ultrastructure*; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D011972:Receptor, Insulin / Q000187:drug effects / Q000378:metabolism*; D015398:Signal Transduction; D014443:Tyrosine / Q000378:metabolism
D000199:Actins; D015815:Cell Adhesion Molecules; D015638:Cytochalasin D; D014443:Tyrosine; D002766:Cholecystokinin; D011505:Protein-Tyrosine Kinases; D011972:Receptor, Insulin; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496052:Ptk2 protein, rat