Contact-Dependent Protein Secretion in Porphyromonas gingivalis

Porphyromonas gingivalis can induce its uptake by host epithelial cells; however, the nature and role of the P. gingivalis molecules involved in this invasion process have yet to be determined. In this study, modulation of secreted P. gingivalis proteins following association with gingival epithelial cells was investigated. Western immunoblot analysis showed that contact with epithelial cells or epithelial cell growth media induces P. gingivalis 33277 to secrete several proteins with molecular masses between 35 and 95 kDa. Secretion of the Arg-gingipain and Lys-gingipain proteases was repressed under these conditions. The contact-induced secreted protein profile was altered in Arg-gingipain-deficient and Lys-gingipain-deficient mutants, indicating a possible role for these proteases in the secretion pathway. The P. gingivalis contact-dependent protein secretion pathway differs to some extent from type III protein secretion pathways in enteric pathogens, as a gene homologous to the invA family genes was not detected in P. gingivalis. The secreted proteins of P. gingivalis may play a role in the interactions of the organism with host cells.

牙龈卟啉单胞菌（Porphyromonas gingivalis）可诱导宿主上皮细胞对其的摄取，然而，参与这一侵袭过程的牙龈卟啉单胞菌分子的本质与作用仍有待明确。本研究针对牙龈卟啉单胞菌与牙龈上皮细胞结合后其分泌蛋白的调控情况展开了探究。蛋白质免疫印迹（Western immunoblot）分析结果显示，与上皮细胞或上皮细胞培养液接触后，牙龈卟啉单胞菌33277菌株可分泌多种分子量介于35~95 kDa的蛋白质。在此条件下，精氨酸牙龈素（Arg-gingipain）与赖氨酸牙龈素（Lys-gingipain）这两种蛋白酶的分泌受到抑制。精氨酸牙龈素缺陷型与赖氨酸牙龈素缺陷型突变株的接触诱导分泌蛋白谱发生了改变，这表明这两种蛋白酶可能在分泌通路中发挥作用。牙龈卟啉单胞菌的接触依赖性蛋白分泌通路在一定程度上不同于肠道病原体的Ⅲ型蛋白分泌通路，因为在牙龈卟啉单胞菌中未检测到与invA家族基因同源的基因。牙龈卟啉单胞菌的分泌蛋白可能在该菌与宿主细胞的相互作用中发挥作用。