TY - JOUR
T1 - Agonist-independent activation of Src tyrosine kinase by a cholecystokinin-2 (CCK2) receptor splice variant
AU - Olszewska-Pazdrak, Barbara
AU - Townsend, Courtney M.
AU - Hellmich, Mark R.
PY - 2004/9/24
Y1 - 2004/9/24
N2 - Src activity is elevated in a majority of colonic and pancreatic cancers and is associated with late stage aggressive cancers. However, the mechanisms leading to its increased activity remain largely undefined. Agonist binding to the cholecystokinin-2 (CCK2/gastrin receptor (CCK2R), a G-protein-coupled receptor, increases Src activity in a variety of normal and neoplastic cell lines. Recently, we and others (Hellmich, M. R., Rui, X. L., Hellmich, H. L., Fleming, R. Y., Evers, B. M., and Townsend, C. M., Jr. (2000) J. Biol. Chem. 275, 32122-32128; Ding, W. Q., Kuntz, S. M., and Miller, L. J. (2002) Cancer Res. 62, 047-952; Smith, J. P., Verderame, M. F., HeLaughlin, P., Martenis, M., Ballard, E., and Zagon, I. S. (2002) Int. J. Mol. Med. 10, 689-694) have identified a splice variant of CCK2R, called CCK 2i4svR, that is expressed in human colorectal and pancreatic cancers but not by cells of the adjacent nonmalignant tissue. Compared with CCK 2R, CCK2i4svR contains an additional 69 amino acids within its third intracellular loop (3il) domain. Because CCK2i4svR is the only splice variant expressed in some human colon and pancreatic cancers, we questioned whether CCK2i4svR could regulate Src activity. Stably transfected HEK293 cells were used because, unlike many cancer-derived cells, they have a low level of basal Src activity. We report that, in contrast to CCK2R, CCK2i4svR activates Src kinase in the absence of agonist stimulation. In vitro kinase assay of immunoprecipitated receptor protein showed a 6-8-fold increase in Src kinase activity associated with CCK2i4svR compared with CCK2R. Expression of the 3il domain of the CCK2i4svR alone was sufficient to partially activate Src kinase. Together, these data sapport the hypothesis that the increased Src activity observed in some pancreatic and colorectal cancers is due, in part, to the co-expression of CCK2i4svR.
AB - Src activity is elevated in a majority of colonic and pancreatic cancers and is associated with late stage aggressive cancers. However, the mechanisms leading to its increased activity remain largely undefined. Agonist binding to the cholecystokinin-2 (CCK2/gastrin receptor (CCK2R), a G-protein-coupled receptor, increases Src activity in a variety of normal and neoplastic cell lines. Recently, we and others (Hellmich, M. R., Rui, X. L., Hellmich, H. L., Fleming, R. Y., Evers, B. M., and Townsend, C. M., Jr. (2000) J. Biol. Chem. 275, 32122-32128; Ding, W. Q., Kuntz, S. M., and Miller, L. J. (2002) Cancer Res. 62, 047-952; Smith, J. P., Verderame, M. F., HeLaughlin, P., Martenis, M., Ballard, E., and Zagon, I. S. (2002) Int. J. Mol. Med. 10, 689-694) have identified a splice variant of CCK2R, called CCK 2i4svR, that is expressed in human colorectal and pancreatic cancers but not by cells of the adjacent nonmalignant tissue. Compared with CCK 2R, CCK2i4svR contains an additional 69 amino acids within its third intracellular loop (3il) domain. Because CCK2i4svR is the only splice variant expressed in some human colon and pancreatic cancers, we questioned whether CCK2i4svR could regulate Src activity. Stably transfected HEK293 cells were used because, unlike many cancer-derived cells, they have a low level of basal Src activity. We report that, in contrast to CCK2R, CCK2i4svR activates Src kinase in the absence of agonist stimulation. In vitro kinase assay of immunoprecipitated receptor protein showed a 6-8-fold increase in Src kinase activity associated with CCK2i4svR compared with CCK2R. Expression of the 3il domain of the CCK2i4svR alone was sufficient to partially activate Src kinase. Together, these data sapport the hypothesis that the increased Src activity observed in some pancreatic and colorectal cancers is due, in part, to the co-expression of CCK2i4svR.
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U2 - 10.1074/jbc.C400208200
DO - 10.1074/jbc.C400208200
M3 - Article
C2 - 15292208
AN - SCOPUS:4644315285
SN - 0021-9258
VL - 279
SP - 40400
EP - 40404
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 39
ER -