TY - JOUR
T1 - FACIN, a double-edged sword of the emerging periodontal pathogen filifactor alocis
T2 - A metabolic enzyme moonlighting as a complement inhibitor
AU - Jusko, Monika
AU - Miedziak, Beata
AU - Ermert, David
AU - Magda, Michal
AU - King, Ben C.
AU - Bielecka, Ewa
AU - Riesbeck, Kristian
AU - Eick, Sigrun
AU - Potempa, Jan
AU - Blom, Anna M.
PY - 2016/10/15
Y1 - 2016/10/15
N2 - Periodontal disease is one of the most common inflammatory infectious diseases worldwide and it is associated with other syndromes, such as cardiovascular disease or rheumatoid arthritis. Recent advances in sequencing allowed for identification of novel periodontopathogens such as Gram-positive Filifactor alocis, but its virulence mechanisms remain largely unknown.We confirmed that F. alocis is a prevalent species in periodontitis patients, and we also observed strong correlation of this bacterium with clinical parameters, highlighting its role in the pathogenesis of the disease. Further, we found that preincubation of human serum with F. alocis resulted in abolished bactericidal activity and that F. alocis was surviving readily in full blood. We demonstrated that one of the key contributors to F. alocis complement resistance is a unique protein, FACIN (F. alocis complement inhibitor), which binds to C3, resulting in suppression of all complement pathways. Interestingly, FACIN is a nonclassical cell surface protein, a cytosolic enzyme acetylornithine transaminase, for which we now identified a moonlighting function. FACIN binds to C3 alone, but more importantly it also captures activated complement factor 3 within the complex with factor B, thereby locking in the convertase in an inactive state. Because of the indispensable role of alternative pathway convertase in amplifying complement cascades, its inhibition by FACIN results in a very potent downregulation of activated complement factor 3 opsonization on the pathogen surface, accompanied by reduction of downstream C5 cleavage.
AB - Periodontal disease is one of the most common inflammatory infectious diseases worldwide and it is associated with other syndromes, such as cardiovascular disease or rheumatoid arthritis. Recent advances in sequencing allowed for identification of novel periodontopathogens such as Gram-positive Filifactor alocis, but its virulence mechanisms remain largely unknown.We confirmed that F. alocis is a prevalent species in periodontitis patients, and we also observed strong correlation of this bacterium with clinical parameters, highlighting its role in the pathogenesis of the disease. Further, we found that preincubation of human serum with F. alocis resulted in abolished bactericidal activity and that F. alocis was surviving readily in full blood. We demonstrated that one of the key contributors to F. alocis complement resistance is a unique protein, FACIN (F. alocis complement inhibitor), which binds to C3, resulting in suppression of all complement pathways. Interestingly, FACIN is a nonclassical cell surface protein, a cytosolic enzyme acetylornithine transaminase, for which we now identified a moonlighting function. FACIN binds to C3 alone, but more importantly it also captures activated complement factor 3 within the complex with factor B, thereby locking in the convertase in an inactive state. Because of the indispensable role of alternative pathway convertase in amplifying complement cascades, its inhibition by FACIN results in a very potent downregulation of activated complement factor 3 opsonization on the pathogen surface, accompanied by reduction of downstream C5 cleavage.
UR - http://www.scopus.com/inward/record.url?scp=84991449356&partnerID=8YFLogxK
U2 - 10.4049/jimmunol.1600739
DO - 10.4049/jimmunol.1600739
M3 - Article
C2 - 27638863
AN - SCOPUS:84991449356
SN - 0022-1767
VL - 197
SP - 3245
EP - 3259
JO - Journal of Immunology
JF - Journal of Immunology
IS - 8
ER -