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J. Biol. Chem., Vol. 278, Issue 21, 19008-19016, May 23, 2003

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Phosphospecific Site Tyrosine Phosphorylation of p125^FAK and Proline-rich Kinase 2 Is Differentially Regulated by Cholecystokinin Receptor Type A Activation in Pancreatic Acini^*

Andrea Pace , Luis J. García-Marin , Jose A. Tapia , María J. Bragado ¶ and Robert T. Jensen  ||

From the Digestive Diseases Branch, NIDDK, National Institutes of Health, Bethesda, Maryland 20892, Departamento de Fisiología, Molecular y Genética, Universidad de Extremadura, Cáceres 10071, Spain, ^¶ Departamento de Bioquímica, Biología Molecular y Genética, Universidad de Extremadura, Cáceres 10071, Spain

The focal adhesion kinases, p125^FAK and proline-rich kinase 2 (PYK2), are involved in numerous processes as adhesion, cytoskeletal changes, and growth. These kinases have 45% homology and share three tyrosine phosphorylation (TyrP) sites. Little information exists on the ability of stimulants to cause TyrP of each kinase site and the cellular mechanism involved. We explored the ability of the neurotransmitter/hormone, CCK, to stimulate TyrP at each site. In rat pancreatic acini, CCK stimulated TyrP at each site in both kinases. TyrP was rapid except for pY397FAK. The magnitude of TyrP differed with the different FAK and PYK2 sites. The CCK dose-response curve for TyrP for sites in each kinase was similar. CCK-JMV, an agonist of the high affinity receptor state and antagonist of the low affinity receptor state, was less efficacious than CCK at each FAK/PYK2 site and inhibited CCK maximal stimulation. Thapsigargin decreased CCK-stimulated TyrP of pY402PYK2 and pY925FAK but not the other sites. GF109203X reduced TyrP of only the PYK2 sites, pY402 and pY580. GF109203X with thapsigargin decreased TyrP of pY402PYK2 and the three FAK sites more than either inhibitor alone. Basal TyrP of pY397FAK was greater than other sites. These results demonstrate that CCK stimulates tyrosine phosphorylation of each of the three homologous phosphorylation sites in FAK and PYK2. However, CCK-stimulated TyrP at these sites differs in kinetics, magnitude, and participation of the high/low affinity receptor states and by protein kinase C and [Ca²⁺]_i. These results show that phosphorylation of these different sites is differentially regulated and involves different intracellular mechanisms in the same cell.

Received for publication, January 24, 2003 , and in revised form, March 19, 2003.

^|| To whom correspondence should be addressed: NIH/NIDDK/DDB, Bldg. 10, Rm. 9C-103, 10 Center Dr. MSC 1804, Bethesda, MD 20892-1804. Tel.: 301-496-4201; Fax: 301-402-0600; E-mail: robertj{at}bdg10.niddk.nih.gov.

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