Tsuneizumi Kenta, Kasamatsu Atsushi, Saito Tomoaki, Fukushima Reo, Taga Yuki, Mizuno Kazunori, Sunohara Masataka, Uzawa Katsuhiro, Yamauchi Mitsuo
Department of Oral Science, Graduate School of Medicine, Chiba University, Chiba, Japan.
Department of Dentistry and Oral-Maxillofacial Surgery, Chiba University Hospital, Chiba, Japan.
Biochem Biophys Rep. 2024 Jul 19;39:101790. doi: 10.1016/j.bbrep.2024.101790. eCollection 2024 Sep.
Lysyl hydroxylase 2 (LH2) catalyzes the hydroxylation of lysine residues in the telopeptides of type I collagen. This modification is critical for the formation of stable hydroxylysine-aldehyde derived collagen cross-links, thus, for the stability of collagen fibrils. Though dysfunction of LH2 causes Bruck syndrome, recessive osteogenesis imperfecta with joint contracture, the molecular mechanisms by which LH2 affects bone formation are still not well understood. Since the knockout mice are embryonically lethal, we generated bone-specific LH2 conditional knockout mice (bsLH2-cKO) using the osteocalcin-Cre/loxP system, and evaluated phenotypes of femurs. LH2 mRNA and protein levels assessed by qPCR, immunohistochemistry and Data Independent Acquisition proteomics were all markedly low in bsLH2-cKO femurs when compared to controls. Lysine hydroxylation of both carboxy- and amino-terminal telopeptides of an α1(I) chain were significantly diminished resulting in reduction of the hydroxylysine-aldehyde derived cross-links. The collagen fibrils in bsLH2-cKO appeared to be thicker, often fused and irregular when compared to controls. In addition, bone mineral density and mechanical properties of bsLH2-cKO femurs were significantly impaired. Taken together, these data demonstrate that LH2-catalyzed modification and consequent cross-linking of collagen are critical for proper bone formation and mechanical strength.
赖氨酰羟化酶2（LH2）催化I型胶原蛋白端肽中赖氨酸残基的羟基化。这种修饰对于稳定的羟赖氨酸 - 醛衍生的胶原蛋白交联的形成至关重要，因此对于胶原纤维的稳定性也至关重要。虽然LH2功能障碍会导致布鲁克综合征，即伴有关节挛缩的隐性成骨不全症，但LH2影响骨形成的分子机制仍未完全了解。由于基因敲除小鼠在胚胎期致死，我们使用骨钙素 - Cre/loxP系统生成了骨特异性LH2条件性敲除小鼠（bsLH2 - cKO），并评估了股骨的表型。与对照组相比，通过qPCR、免疫组织化学和数据非依赖采集蛋白质组学评估的bsLH2 - cKO股骨中LH2 mRNA和蛋白质水平均显著降低。α1（I）链的羧基末端和氨基末端端肽的赖氨酸羟基化均显著减少，导致羟赖氨酸 - 醛衍生交联减少。与对照组相比，bsLH2 - cKO中的胶原纤维似乎更粗，常常融合且不规则。此外，bsLH2 - cKO股骨的骨矿物质密度和力学性能显著受损。综上所述，这些数据表明LH2催化的胶原蛋白修饰及其随后的交联对于正常的骨形成和力学强度至关重要。
