TY - JOUR
T1 - An essential role for calcium flux in phagocytes for apoptotic cell engulfment and the anti-inflammatory response
AU - Gronski, M. A.
AU - Kinchen, J. M.
AU - Juncadella, I. J.
AU - Franc, N. C.
AU - Ravichandran, K. S.
N1 - Funding Information:
Acknowledgements. We thank the members of the Ravichandran and Franc labs and Dr. D Haverstick for helpful discussions. We gratefully acknowledge the help of Marcin Iwanicki with the calcium experiments. This work was supported by grants from the National Institutes of Health (NIGMS) and American Asthma Foundation to KSR, and by post-doctoral fellowships from the Natural Sciences and Engineering Research Council of Canada (NSERC) to MAG and the Arthritis Foundation to JMK, as well as Immunology Training Grants from the NIAID (National Institutes of Health, USA) to IJJ and JMK.
PY - 2009
Y1 - 2009
N2 - Cells undergo programmed cell death/apoptosis throughout the lifespan of an organism. The subsequent immunologically silent removal of apoptotic cells plays a role in the maintenance of tolerance; defects in corpse clearance have been associated with autoimmune disease. A number of receptors and signaling molecules involved in this process have been identified, but intracellular signaling downstream of corpse recognition is only now being defined. Calcium plays a key role as a second messenger in many cell types, leading to the activation of downstream molecules and eventual transcription of effector genes; however, the role of calcium signaling during apoptotic cell removal is unclear. Here, using studies in cell lines and in the context of a whole organism, we show that apoptotic cell recognition induces both an acute and sustained calcium flux within phagocytes and that the genes required for calcium flux are essential for engulfment. Furthermore, we provide evidence that both the release of calcium from the endoplasmic reticulum and the entry of extracellular calcium through CRAC channels into the phagocytes are important during engulfment. Moreover, knockdown in Caenorhabditis elegans of stim-1 and jph-1, two genes linked to the entry of extracellular calcium into cells, led to increased persistence of apoptotic cells in the nematode. Loss of these genes seemed to affect early signaling events, leading to a decreased enrichment of actin adjacent to the apoptotic cell during corpse removal. We also show that calcium is crucial for the secretion of TGF-β by the phagocytes during the engulfment of apoptotic cells. Taken together, these data point to an earlier unappreciated and evolutionarily conserved role for calcium flux at two distinguishable steps: the formation of the phagocytic cup and the internalization of the apoptotic cell, and the anti-inflammatory signaling induced in phagocytes by contact with apoptotic cells.
AB - Cells undergo programmed cell death/apoptosis throughout the lifespan of an organism. The subsequent immunologically silent removal of apoptotic cells plays a role in the maintenance of tolerance; defects in corpse clearance have been associated with autoimmune disease. A number of receptors and signaling molecules involved in this process have been identified, but intracellular signaling downstream of corpse recognition is only now being defined. Calcium plays a key role as a second messenger in many cell types, leading to the activation of downstream molecules and eventual transcription of effector genes; however, the role of calcium signaling during apoptotic cell removal is unclear. Here, using studies in cell lines and in the context of a whole organism, we show that apoptotic cell recognition induces both an acute and sustained calcium flux within phagocytes and that the genes required for calcium flux are essential for engulfment. Furthermore, we provide evidence that both the release of calcium from the endoplasmic reticulum and the entry of extracellular calcium through CRAC channels into the phagocytes are important during engulfment. Moreover, knockdown in Caenorhabditis elegans of stim-1 and jph-1, two genes linked to the entry of extracellular calcium into cells, led to increased persistence of apoptotic cells in the nematode. Loss of these genes seemed to affect early signaling events, leading to a decreased enrichment of actin adjacent to the apoptotic cell during corpse removal. We also show that calcium is crucial for the secretion of TGF-β by the phagocytes during the engulfment of apoptotic cells. Taken together, these data point to an earlier unappreciated and evolutionarily conserved role for calcium flux at two distinguishable steps: the formation of the phagocytic cup and the internalization of the apoptotic cell, and the anti-inflammatory signaling induced in phagocytes by contact with apoptotic cells.
UR - http://www.scopus.com/inward/record.url?scp=70349168768&partnerID=8YFLogxK
U2 - 10.1038/cdd.2009.55
DO - 10.1038/cdd.2009.55
M3 - Article
C2 - 19461656
AN - SCOPUS:70349168768
SN - 1350-9047
VL - 16
SP - 1323
EP - 1331
JO - Cell Death and Differentiation
JF - Cell Death and Differentiation
IS - 10
ER -