Article ; Online: Surfactant protein D regulates caspase-8-mediated cascade of the intrinsic pathway of apoptosis while promoting bleb formation.
2017 Volume 92, Page(s) 190–198
Abstract: Surfactant-associated protein D (SP-D) is a soluble innate immune collectin present on many mucosal surfaces. We recently showed that SP-D suppresses the extrinsic pathway of apoptosis by downregulating caspase-8 activation. However, the effects of SP-D ... ...
Abstract | Surfactant-associated protein D (SP-D) is a soluble innate immune collectin present on many mucosal surfaces. We recently showed that SP-D suppresses the extrinsic pathway of apoptosis by downregulating caspase-8 activation. However, the effects of SP-D on the intrinsic pathway of apoptosis are not clearly understood. In the intrinsic pathway, cytochrome c is released by mitochondria into the cytoplasm. Oxidation of cytochrome c by cytochrome c oxidase activates the apoptosome and caspase-9 cascade. Both caspase-8- and caspase-9-mediated branches are activated in the intrinsic pathway of apoptosis; however, little is known about the relevance of the caspase-8 pathway in this context. Here we studied the effects of SP-D on different branches of the intrinsic pathway of apoptosis using UV-irradiated Jurkat T-cells. We found that SP-D does not inhibit the caspase-9 branch of apoptosis and the relevance of the caspase-8-related branch became apparent when the caspase-9 pathway was inhibited by blocking cytochrome c oxidase. Under these conditions, SP-D reduces the activation of caspase-8, executioner caspase-3 and exposure of phosphatidylserine (PS) on the membranes of dying cells. By contrast, SP-D increases the formation of nuclear and membrane blebs. Inhibition of caspase-8 confirms the effect of SP-D is unique to the caspase-8 pathway. Overall, SP-D suppresses certain aspects of the intrinsic pathway of apoptosis via reduction of caspase-8 activation and PS flipping while at the same time increasing membrane and nuclear bleb formation. This novel regulatory aspect of SP-D could help to regulate intrinsic pathway of apoptosis to promote effective blebbing and breakdown of dying cells. |
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MeSH term(s) | Apoptosis/immunology ; Caspase 3/immunology ; Caspase 8/immunology ; Caspase 9/immunology ; Cell Membrane Structures/immunology ; Cytochromes c/immunology ; Humans ; Jurkat Cells ; Nuclear Envelope/immunology ; Pulmonary Surfactant-Associated Protein D/immunology ; Signal Transduction/immunology |
Chemical Substances | Pulmonary Surfactant-Associated Protein D ; Cytochromes c (9007-43-6) ; CASP3 protein, human (EC 3.4.22.-) ; CASP8 protein, human (EC 3.4.22.-) ; CASP9 protein, human (EC 3.4.22.-) ; Caspase 3 (EC 3.4.22.-) ; Caspase 8 (EC 3.4.22.-) ; Caspase 9 (EC 3.4.22.-) |
Language | English |
Publishing date | 2017-11-04 |
Publishing country | England |
Document type | Journal Article ; Research Support, Non-U.S. Gov't |
ZDB-ID | 424427-8 |
ISSN | 1872-9142 ; 0161-5890 |
ISSN (online) | 1872-9142 |
ISSN | 0161-5890 |
DOI | 10.1016/j.molimm.2017.10.016 |
Database | MEDical Literature Analysis and Retrieval System OnLINE |
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