TY - JOUR

T1 - Mitochondria and the lectin pathway of complement

AU - Brinkmann, Christel R

AU - Jensen, Lisbeth

AU - Dagnaes-Hansen, Frederik

AU - Holm, Ida E

AU - Endo, Yuichi

AU - Fujita, Teizo

AU - Thiel, Steffen

AU - Jensenius, Jens C

AU - Degn, Søren E

PY - 2013

Y1 - 2013

N2 - Mitochondria, the powerhouses of our cells, are remnants of a eubacterial endosymbiont. Notwithstanding the evolutionary time that has passed since the initial endosymbiotic event, mitochondria have retained many hallmarks of their eubacterial origin. Recent studies have indicated that during perturbations of normal homeostasis, such as following acute trauma leading to massive necrosis and release of mitochondria, the immune system might mistake symbiont for enemy and initiate an inappropriate immune response. The innate immune system is the first line of defense against invading microbial pathogens, and as such is the primary suspect in the recognition of mitochondria-derived danger-associated molecular patterns (DAMPs) and initiation of an aberrant response. Conversely, innate immune mechanisms are also central to non-inflammatory clearance of innocuous agents. Here we investigated the role of a central humoral component of innate immunity, the lectin pathway of complement, in recognition of mitochondria in vitro and in vivo. We found that the soluble pattern-recognition molecules (PRMs), mannan-binding lectin (MBL), L-ficolin and M-ficolin were able to recognize mitochondria. Furthermore, MBL in complex with MBL-associated serine protease 2 (MASP-2) was able to activate the lectin pathway and deposit C4 onto mitochondria, suggesting that these molecules are either involved in homeostatic clearance of mitochondria or induction of untoward inflammatory reactions. We found that following mitochondrial challenge, C3 was consumed in vivo in the absence of overt inflammation, indicating a potential role of complement in non-inflammatory clearance of mitochondria. Thus, we report here the first indication of involvement of the lectin pathway in mitochondrial immune handling.

AB - Mitochondria, the powerhouses of our cells, are remnants of a eubacterial endosymbiont. Notwithstanding the evolutionary time that has passed since the initial endosymbiotic event, mitochondria have retained many hallmarks of their eubacterial origin. Recent studies have indicated that during perturbations of normal homeostasis, such as following acute trauma leading to massive necrosis and release of mitochondria, the immune system might mistake symbiont for enemy and initiate an inappropriate immune response. The innate immune system is the first line of defense against invading microbial pathogens, and as such is the primary suspect in the recognition of mitochondria-derived danger-associated molecular patterns (DAMPs) and initiation of an aberrant response. Conversely, innate immune mechanisms are also central to non-inflammatory clearance of innocuous agents. Here we investigated the role of a central humoral component of innate immunity, the lectin pathway of complement, in recognition of mitochondria in vitro and in vivo. We found that the soluble pattern-recognition molecules (PRMs), mannan-binding lectin (MBL), L-ficolin and M-ficolin were able to recognize mitochondria. Furthermore, MBL in complex with MBL-associated serine protease 2 (MASP-2) was able to activate the lectin pathway and deposit C4 onto mitochondria, suggesting that these molecules are either involved in homeostatic clearance of mitochondria or induction of untoward inflammatory reactions. We found that following mitochondrial challenge, C3 was consumed in vivo in the absence of overt inflammation, indicating a potential role of complement in non-inflammatory clearance of mitochondria. Thus, we report here the first indication of involvement of the lectin pathway in mitochondrial immune handling.

U2 - 10.1074/jbc.M112.430249

DO - 10.1074/jbc.M112.430249

M3 - Journal article

C2 - 23378531

JO - Journal of Biological Chemistry

JF - Journal of Biological Chemistry

SN - 0021-9258

ER -