Functional cross-talk between beta-catenin and NFkappaB signaling pathways in colonic crypts of mice in response to progastrin.
We recently reported a critical role of NFkappaB in mediating hyperproliferative and anti-apoptotic effects of progastrin on proximal colonic crypts of transgenic mice overexpressing progastrin (Fabp-PG mice). We now report activation of beta-catenin in colonic crypts of mice in response to chronic (Fabp-PG mice) and acute (wild type FVB/N mice) progastrin stimulation. Significant increases were measured in relative levels of cellular and nuclear beta-catenin and pbeta-cat45 in proximal colonic crypts of Fabp-PG mice compared with that in wild type littermates. Distal colonic crypts were less responsive. Interestingly, beta-catenin activation was downstream of IKKalpha,beta/NFkappaB, because treatment of Fabp-PG mice with the NFkappaB essential modulator (NEMO) peptide (inhibitor of IKKalpha,beta/NFkappaB activation) significantly blocked increases in cellular/nuclear levels of total beta-catenin/pbeta-cat45/and pbeta-cat552 in proximal colons. Cellular levels of pbeta-cat33,37,41, however, increased in proximal colons in response to NEMO, probably because of a significant increase in pGSK-3betaTyr216, facilitating degradation of beta-catenin. NEMO peptide significantly blocked increases in cyclin D1 expression, thereby, abrogating hyperplasia of proximal crypts. Goblet cell hyperplasia in colonic crypts of Fabp-PG mice was abrogated by NEMO treatment, suggesting a cross-talk between the NFkappaB/beta-catenin and Notch pathways. Cellular proliferation and crypt lengths increased significantly in proximal but not distal crypts of FVB/N mice injected with 1 nM progastrin associated with a significant increase in cellular/nuclear levels of total beta-catenin and cyclin D1. Thus, intracellular signals, activated in response to acute and chronic stimulation with progastrin, were similar and specific to proximal colons. Our studies suggest a novel possibility that activation of beta-catenin, downstream to the IKKalpha,beta/NFkappaB pathway, may be integral to the hyperproliferative effects of progastrin on proximal colonic crypts.
Umar
Shahid
S
Department of Internal Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104; Internal Medicine, University of Texas Medical Branch, Galveston, Texas 77555.
Sarkar
Shubhashish
S
the Departments of Neuroscience and Cell Biology, Galveston, Texas 77555.
Wang
Yu
Y
the Departments of Neuroscience and Cell Biology, Galveston, Texas 77555.
Singh
Pomila
P
the Departments of Neuroscience and Cell Biology, Galveston, Texas 77555.
D000818:Animals; D049109:Cell Proliferation; D003106:Colon / Q000378:metabolism* / Q000473:pathology; D019938:Cyclin D1 / Q000096:biosynthesis; D005755:Gastrins / Q000378:metabolism / Q000502:physiology*; D005786:Gene Expression Regulation; D020397:Goblet Cells / Q000378:metabolism; D006720:Homozygote; D006965:Hyperplasia; D051379:Mice; D008822:Mice, Transgenic; D008954:Models, Biological; D016328:NF-kappa B / Q000378:metabolism*; D011498:Protein Precursors / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction; D051176:beta Catenin / Q000378:metabolism*
D005755:Gastrins; D016328:NF-kappa B; D011498:Protein Precursors; D051176:beta Catenin; D019938:Cyclin D1; C013706:big gastrin