title: Caspase-6 mediated cleavage of guanylate cyclase alpha 1 during deoxycholate-induced apoptosis: protective role of the nitric oxide signaling module.
abstract: Hydrophobic bile acids such as deoxycholate are known tumor promoters in the gastrointestinal tract. We have previously shown that deoxycholate induces apoptosis in colon epithelial cells and that these cells can be made resistant to deoxycholate-induced apoptosis. We now show that the nitric oxide synthase/nitric oxide/guanylate cyclase/cyclic guanosine monophosphate/cGMP-activated protein kinase (NOS/NO/GC/cGMP/PKG) signaling module contributes, in part, to the observed resistance of the cultured DOC-resistant colon epithelial cells (HCT-116R) using pharmacological inhibitors/antagonists (NS2028, Rp-8pCPT-cGMP, KT5823) of members of this signaling module. A novel finding from this study is the caspase-6 mediated cleavage of guanylate cyclase alpha 1 during deoxycholate-induced apoptosis of deoxycholate-sensitive HCT-116SA cells and the absence of guanylate cyclase alpha 1 cleavage in deoxycholate-treated HCT-116R resistant cells using Western blot analyses. This cleavage was specific to caspases as lysosomal, proteasomal, serine protease, cathepsin and calpain inhibitors failed to prevent the cleavage, whereas a general caspase inhibitor and a specific caspase-6 inhibitor did prevent guanylate cyclase alpha 1 cleavage.
authors.affiliation: Department of Microbiology and Immunology, College of Medicine, University of Arizona, Tucson, Arizona 85724, USA. cpayne@u.arizona.edu
authors.forename: C M
authors.initials: CM
authors.lastname: Payne
authors.forename: C N
authors.initials: CN
authors.lastname: Waltmire
authors.forename: C
authors.initials: C
authors.lastname: Crowley
authors.forename: C L
authors.initials: CL
authors.lastname: Crowley-Weber
authors.forename: K
authors.initials: K
authors.lastname: Dvorakova
authors.forename: H
authors.initials: H
authors.lastname: Bernstein
authors.forename: C
authors.initials: C
authors.lastname: Bernstein
authors.forename: H
authors.initials: H
authors.lastname: Holubec
authors.forename: H
authors.initials: H
authors.lastname: Garewal
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D053178:Caspase 6; D020169:Caspases / Q000378:metabolism*; D003110:Colonic Neoplasms / Q000201:enzymology*; D006152:Cyclic GMP / Q000378:metabolism; D003840:Deoxycholic Acid / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000201:enzymology*; D006162:Guanylate Cyclase / Q000378:metabolism*; D006801:Humans; D020030:Nitric Oxide Donors / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D004791:Enzyme Inhibitors; D020030:Nitric Oxide Donors; D017382:Reactive Oxygen Species; D003840:Deoxycholic Acid; D019001:Nitric Oxide Synthase; C505514:CASP6 protein, human; D053178:Caspase 6; D020169:Caspases; D006162:Guanylate Cyclase; D006152:Cyclic GMP