TY - JOUR
T1 - Nucleotides released by apoptotic cells act as a find-me signal to promote phagocytic clearance
AU - Elliott, Michael R.
AU - Chekeni, Faraaz B.
AU - Trampont, Paul C.
AU - Lazarowski, Eduardo R.
AU - Kadl, Alexandra
AU - Walk, Scott F.
AU - Park, Daeho
AU - Woodson, Robin I.
AU - Ostankovich, Marina
AU - Sharma, Poonam
AU - Lysiak, Jeffrey J.
AU - Harden, T. Kendall
AU - Leitinger, Norbert
AU - Ravichandran, Kodi S.
N1 - Funding Information:
Acknowledgements We thank K. Rock, C. Borowski and members of the Ravichandran laboratory for helpful suggestions; I. Juncadella for lung epithelial cells; K. Lauber and S. Wesselborg for providing MCF-7/caspase-3 cells; and R. Tacke for assistance with primary monocyte experiments. This work was supported by Public Health Service grants from the National Institutes of Health (to K.S.R. and N.L.), the American Cancer Society (to M.R.E.) and the University of Virginia Farrow Fellowship (to M.R.E.).
PY - 2009/9/10
Y1 - 2009/9/10
N2 - Phagocytic removal of apoptotic cells occurs efficiently in vivo such that even in tissues with significant apoptosis, very few apoptotic cells are detectable. This is thought to be due to the release of find-me signals by apoptotic cells that recruit motile phagocytes such as monocytes, macrophages and dendritic cells, leading to the prompt clearance of the dying cells. However, the identity and in vivo relevance of such find-me signals are not well understood. Here, through several lines of evidence, we identify extracellular nucleotides as a critical apoptotic cell find-me signal. We demonstrate the caspase-dependent release of ATP and UTP (in equimolar quantities) during the early stages of apoptosis by primary thymocytes and cell lines. Purified nucleotides at these concentrations were sufficient to induce monocyte recruitment comparable to that of apoptotic cell supernatants. Enzymatic removal of ATP and UTP (by apyrase or the expression of ectopic CD39) abrogated the ability of apoptotic cell supernatants to recruit monocytes in vitro and in vivo. We then identified the ATP/UTP receptor P2Y 2 as a critical sensor of nucleotides released by apoptotic cells using RNA interference-mediated depletion studies in monocytes, and macrophages from P2Y2 -null mice. The relevance of nucleotides in apoptotic cell clearance in vivo was revealed by two approaches. First, in a murine air-pouch model, apoptotic cell supernatants induced a threefold greater recruitment of monocytes and macrophages than supernatants from healthy cells did; this recruitment was abolished by depletion of nucleotides and was significantly decreased in P2Y2 -/- (also known as P2ry2 -/-) mice. Second, clearance of apoptotic thymocytes was significantly impaired by either depletion of nucleotides or interference with P2Y receptor function (by pharmacological inhibition or in P2Y2 -/- mice). These results identify nucleotides as a critical find-me cue released by apoptotic cells to promote P2Y 2-dependent recruitment of phagocytes, and provide evidence for a clear relationship between a find-me signal and efficient corpse clearance in vivo.
AB - Phagocytic removal of apoptotic cells occurs efficiently in vivo such that even in tissues with significant apoptosis, very few apoptotic cells are detectable. This is thought to be due to the release of find-me signals by apoptotic cells that recruit motile phagocytes such as monocytes, macrophages and dendritic cells, leading to the prompt clearance of the dying cells. However, the identity and in vivo relevance of such find-me signals are not well understood. Here, through several lines of evidence, we identify extracellular nucleotides as a critical apoptotic cell find-me signal. We demonstrate the caspase-dependent release of ATP and UTP (in equimolar quantities) during the early stages of apoptosis by primary thymocytes and cell lines. Purified nucleotides at these concentrations were sufficient to induce monocyte recruitment comparable to that of apoptotic cell supernatants. Enzymatic removal of ATP and UTP (by apyrase or the expression of ectopic CD39) abrogated the ability of apoptotic cell supernatants to recruit monocytes in vitro and in vivo. We then identified the ATP/UTP receptor P2Y 2 as a critical sensor of nucleotides released by apoptotic cells using RNA interference-mediated depletion studies in monocytes, and macrophages from P2Y2 -null mice. The relevance of nucleotides in apoptotic cell clearance in vivo was revealed by two approaches. First, in a murine air-pouch model, apoptotic cell supernatants induced a threefold greater recruitment of monocytes and macrophages than supernatants from healthy cells did; this recruitment was abolished by depletion of nucleotides and was significantly decreased in P2Y2 -/- (also known as P2ry2 -/-) mice. Second, clearance of apoptotic thymocytes was significantly impaired by either depletion of nucleotides or interference with P2Y receptor function (by pharmacological inhibition or in P2Y2 -/- mice). These results identify nucleotides as a critical find-me cue released by apoptotic cells to promote P2Y 2-dependent recruitment of phagocytes, and provide evidence for a clear relationship between a find-me signal and efficient corpse clearance in vivo.
UR - http://www.scopus.com/inward/record.url?scp=70249090374&partnerID=8YFLogxK
U2 - 10.1038/nature08296
DO - 10.1038/nature08296
M3 - Article
C2 - 19741708
AN - SCOPUS:70249090374
SN - 0028-0836
VL - 461
SP - 282
EP - 286
JO - Nature
JF - Nature
IS - 7261
ER -