title: Monocyte Caspase-1 Is Released in a Stable, Active High Molecular Weight Complex Distinct from the Unstable Cell Lysate-Activated Caspase-1.
abstract: Mononuclear phagocytes utilize caspase-1 activation as a means to respond to danger signals. Although caspase-1 was discovered using highly concentrated cell extracts that spontaneously activate caspase-1, it is now clear that in live cell models caspase-1 activation occurs in the process of its cellular release and is not an intracellular event. Therefore, we compared the characteristics of caspase-1 activation in the cell lysate model to that of caspase-1 that is released in response to exogenous inflammasome activation. Whereas both models generated active caspase-1, the cell-lysate induced caspase-1 required highly concentrated cell lysates and had a short half-life (~15 min) whereas, the activation induced released caspase-1 required 2-3 log fold fewer cells and was stable for greater than 12 h. Both forms were able to cleave proIL-1beta but unexpectedly, the released activity was unable to be immunodepleted by caspase-1 antibodies. Size exclusion chromatography identified two antigenic forms of p20 caspase-1 in the activation induced released caspase-1: one at the predicted size of tetrameric, p20/p10 caspase-1 and the other at >200 kDa. However, only the high molecular weight form had stable functional activity. These results suggest that released caspase-1 exists in a unique complex that is functionally stable and protected from immunodepletion whereas cell-extract generated active caspase-1 is rapidly inhibited in the cytosolic milieu.
authors.affiliation: Davis Heart and Lung Research Institute, Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Internal Medicine, Wexner Medical Center, The Ohio State University, 473 W. 12th Avenue, 201 DHLRI, Columbus, OH, United States of America.
authors.forename: Obada R
authors.initials: OR
authors.lastname: Shamaa
authors.affiliation: Davis Heart and Lung Research Institute, Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Internal Medicine, Wexner Medical Center, The Ohio State University, 473 W. 12th Avenue, 201 DHLRI, Columbus, OH, United States of America.
authors.forename: Srabani
authors.initials: S
authors.lastname: Mitra
authors.affiliation: Davis Heart and Lung Research Institute, Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Internal Medicine, Wexner Medical Center, The Ohio State University, 473 W. 12th Avenue, 201 DHLRI, Columbus, OH, United States of America.
authors.forename: Mikhail A
authors.initials: MA
authors.lastname: Gavrilin
authors.affiliation: Davis Heart and Lung Research Institute, Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Internal Medicine, Wexner Medical Center, The Ohio State University, 473 W. 12th Avenue, 201 DHLRI, Columbus, OH, United States of America.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Wewers
mesh_terms: D017209:Apoptosis; D020170:Caspase 1 / Q000737:chemistry / Q000378:metabolism*; D002457:Cell Extracts / Q000737:chemistry; D002460:Cell Line; D002474:Cell-Free System; D004789:Enzyme Activation; D004795:Enzyme Stability; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D058847:Inflammasomes / Q000378:metabolism*; D007425:Intracellular Membranes / Q000201:enzymology / Q000378:metabolism; D009000:Monocytes / Q000201:enzymology / Q000378:metabolism; D011480:Protease Inhibitors / Q000494:pharmacology
chemical_list: D002457:Cell Extracts; D058847:Inflammasomes; D011480:Protease Inhibitors; D020170:Caspase 1