The Msp protein complex and the serine protease dentilisin are the best-characterized virulence factors in Treponema denticola, the major etiological agent of chronic periodontitis. In addition to these outer sheath factors, the cysteine protease dentipain contributes to pathogenicity, but its secretion, processing, cellular localization, and role in T. denticola virulence are not fully understood. In this study, we found that full-sized dentipain (74-kDa) and the 52-kDa truncated form of the enzyme are located, respectively, in the outer sheath derived from T. denticola dentilisin- and the Msp-deficient mutants. Furthermore, dentipain was barely detected in the wild-type strain. These results suggest that dentilisin and Msp, the major outer sheath proteins, are involved in the secretion and maturation of dentipain. Inactivation of the dentipain gene slowed the growth of T. denticola, and the effect was more profound in serum-free medium than in serum-containing medium. Several genes, including those encoding transporters and methyl-accepting chemotaxis proteins, were differentially expressed in the dentipain-deficient mutant. Furthermore, the mutant strain was more hydrophobic than the wild-type strain. Finally, the mutant showed less autoaggregation activity and adhesion to IgG in a serum-free medium than the wild-type strain. These findings suggest that dentipain contributes to the virulence of T. denticola by facilitating adhesion and acquisition of nutrients essential for colonization and proliferation in the gingival crevice under serum-rich conditions.

中文翻译：

---

半胱氨酸蛋白酶牙本质蛋白酶在牙髓密螺旋体中的定位和致病作用

Msp 蛋白复合物和丝氨酸蛋白酶牙菌素是牙髓密螺旋体（慢性牙周炎的主要病原体）中最具特征的毒力因子。除了这些外鞘因子外，半胱氨酸蛋白酶牙本质蛋白酶也有助于致病性，但其分泌、加工、细胞定位和在T. denticola毒力中的作用尚不完全清楚。在这项研究中，我们发现全尺寸牙本质蛋白酶 (74-kDa) 和酶的 52-kDa 截短形式分别位于T. denticola的外鞘中dentilisin 和 Msp 缺陷突变体。此外，在野生型菌株中几乎检测不到牙硫蛋白酶。这些结果表明牙脂溶素和 Msp，主要的外鞘蛋白，参与牙脂蛋白酶的分泌和成熟。dentipain 基因的失活减缓了T. denticola的生长，并且在无血清培养基中效果比在含血清培养基中更显着。几个基因，包括那些编码转运蛋白和甲基接受趋化蛋白的基因，在牙脂蛋白酶缺陷突变体中差异表达。此外，突变菌株比野生型菌株更疏水。最后，与野生型菌株相比，突变体在无血清培养基中表现出更少的自聚集活性和对 IgG 的粘附。这些发现表明，牙脂蛋白酶通过促进粘附和获取在富含血清的条件下在牙龈缝隙中定植和增殖所必需的营养物质，从而促进了T. denticola的毒力。