Title |
Role of bacterial γ-glutamyltranspeptidase as a novel virulence factor in bone-resorbing pathogenesis |
Author |
Jinmoon Kim1,2, Sungil Jang1,3, Aeryun Kim1,3, Hanfu Su1,3, Niluka Gunawardhana1,4, Yeong-Eui Jeon1, Eun Jung Bak1, Ji-Hye Kim5*, and Jeong-Heon Cha1,3* |
Address |
1Department of Oral Biology, Oral Science Research Center, BK21 Plus Project, Yonsei University College of Dentistry, Seoul 03722, Republic of Korea, 2ATGen Ltd, Bundang-gu, Seongnam-si 13488, Gyeonggi-do, 3Department of Applied Life Science, The Graduate School, Yonsei University, Seoul 03722, Republic of Korea, 4OMFS Unit, District General Hospital, Nuwara Eliya, Sri Lanka, 5Department of Dental Hygiene, Jeonju Kijeon College, Jeonju 560-701, Republic of Korea |
Bibliography |
Journal of Microbiology, 54(5),396-402, 2016,
|
DOI |
10.1007/s12275-016-6137-1
|
Key Words |
γ-glutamyltranspeptidase, osteoclastogenesis, Bacillus
subtilis, bone resorption |
Abstract |
Mammalian γ-glutamyltranspeptidase (GGT) has been identified
as a bone-resorbing factor. Since GGT of Bacillus subtilis
exhibits similarity in their primary structure and enzymatic
characteristics with mammalian GGTs, the bone-resorbing
activity of bacterial GGT was examined in this study. Osteoclastogenesis
was performed in a co-culture system of mouse
calvaria-derived osteoblasts and bone marrow cells. A conditioned
medium from GGT-overproducing B. subtilis culture
showed significantly higher activity of osteoclast formation
than a conditioned medium from wild-type B. subtilis culture.
Recombinant GGT (rGGT) of wild-type B. subtilis and an
enzymatic activity-defected rGGT of B. subtilis 2288 mutant
were expressed in Escherichia coli and purified using His tag.
Both purified rGGTs induced similar levels of osteoclastogenesis,
suggesting that B. subtilis GGT possesses virulent boneresorbing
activity and its activity is probably independent of
its enzymatic activity. Furthermore, a recombinant protein of
B. subtilis GGT heavy subunit (Bs rGGT/H) showed strong
activity of osteoclastogenesis while the light subunit failed to
show strong activity, suggesting that the bone-resorbing activity
is mainly located at the heavy subunit. More importantly,
the GGT enzymatic activity may not be required for this virulence
activity since the light subunit contains the catalytic
pocket. In addition, B. subtilis rGGT stimulated mRNA expressions
of receptor activator of nuclear factor kappa-B ligand
(RANKL) and cyclooxygenase-2 (COX-2), while an
osteoprotegerin inhibited the osteoclast formation induced by Bs rGGT/H. This is the first demonstration that bacterial
GGT itself is sufficient to act as a bone-resorbing virulence
factor via RANKL-dependent pathway. Therefore, it can be
hypothesized that GGT of periodontopathic bacteria may play
an important role as a virulence factor in bone destruction. |