Collagen Diversity and Pathobiology in Skeletal Tissues

描述(由申请人提供)：在AR036794的竞争性更新(标题更新以反映特定目标和范围的演变)中，我们重点介绍了一种新发现的胶原纤维多样性调节机制，该机制对于理解骨骼组织分化和病理生物学非常重要。我们有证据表明，3-羟脯氨酸(3Hyp)残基在引导胶原纤维超分子组装方式中起着基础性的作用。第一个线索来自我们的质谱学证明，在CRTAP小鼠和隐性人类成骨不全(OI.)的胶原蛋白中，A1(I)和A1(II)链C末端附近单一的、完全占据的3Hyp位点(P986)不能被羟化。由CRTAP或LEPRE1突变引起。我们现在有证据证明在形成纤维的胶原蛋白中有三类3Hyp位点。例如，II型胶原的第二个部位在玻璃体、半月板和椎间盘中高度羟化，但在透明软骨中不是。第二个位点的序列基序在a2(V)中以D-周期间隔复制，并存在3Hyp，与IV型胶原中的3Hyp基序相似。肌腱胶原蛋白独特地含有第三种类型的3Hyp基序，我们认为这种基序在肌腱、韧带和相关的高张力组织中具有特征和重要的功能。在4个目标下，我们打算积极地追求这一概念，因为它是理解不同细胞类型如何调节不同软骨、骨、肌腱和其他结缔组织之间的异质多聚胶原蛋白组合多样性的核心。如果是正确的，这对脊椎动物胶原蛋白生物学领域也具有改变概念的意义。其临床意义在于为了解成人骨关节炎、关节盘退变及相关的胶原支架功能障碍中软骨及其他低周转率的胶原组织退变的过程提供分子基础。此外，我们认为，充分了解在隐性成骨不全中破坏3-羟基化的影响，将揭示所有形式的OI.共同的脆性骨的分子机制。这些发现对于理解骨基质的质变也具有重要意义，这些质变增加了整个人群骨质疏松性骨折的显著风险，并可能成为新的生物标志物和治疗靶点。 与公共健康相关：目标是了解支配胶原蛋白属性多样性的分子机制，胶原蛋白是构成人体所有主要骨骼组织的结构框架的蛋白质，包括骨、软骨、肌腱和韧带。具体地说，我们的目标是定义使骨胶原矿化、软骨持续一生的生化途径，作为关节、肌腱和韧带的承重面，以传递或抑制高机械负荷而不会失败。利用这一知识，可以预测治疗和预防遗传性和获得性人类骨骼和关节疾病的新目标。

DESCRIPTION (provided by applicant): In this competing renewal of AR036794 (title updated to reflect the evolution in specific aims and scope), we focus on a newly discovered mechanism of regulation of collagen fibril diversity that is important for understanding skeletal tissue differentiation and pathobiology. We have evidence that 3-hydroxproline (3Hyp) residues play a fundamental role in directing the manner of fibrillar collagen supramolecular assembly. The first hint came from our demonstration by mass spectrometry that the single, fully occupied 3Hyp site (P986) near the C-terminus of collagen a1(I) and a1(II) chains fails to be hydroxylated in collagens of the crtap mouse and recessive forms of human osteogenesis imperfecta (O.I.) caused by CRTAP or LEPRE1 mutations. We now have evidence for three classes of 3Hyp site in fibril-forming collagens. For example, a second site in type II collagen is highly hydroxylated in vitreous, meniscus and intervertebral disc but not in hyaline cartilage. The sequence motif of this second site is reproduced at D-periodic intervals in a2(V), with 3Hyp present, and shows similarities to a 3Hyp motif in type IV collagen. Tendon collagen uniquely contains a third type of 3Hyp motif, which we believe is characteristic and functionally important in tendon, ligament and related highly tensile tissues. Under 4 aims, we intend to pursue this concept aggressively since it is central to understanding how different cell types regulate the diversity of heteropolymeric collagen assemblies between different cartilages, bone, tendon and other connective tissues. If correct, it also has concept- changing implications for the field of vertebrate collagen biology. The clinical significance is in providing a molecular basis for understanding processes that cause cartilages and other collagenous tissues of low turnover to degenerate in the adult musculoskeleton in osteoarthritis, disc degeneration and related disorders of collagen framework failure. In addition, a full understanding of the effects of disrupting prolyl 3-hydroxylation in recessive forms of osteogenesis imperfecta we believe will reveal a molecular mechanism for brittle bone common to all forms of O.I. Such findings will also be significant for understanding qualitative changes in bone matrix that add significant risk of osteoporotic fracture in the population as a whole and a potential for novel biomarkers and therapeutic targets. PUBLIC HEALTH RELEVANCE: The goal is to understand molecular mechanisms that govern the diversity in properties of collagen, the protein that forms the structural framework of all major skeletal tissues in the body including bone, cartilages, tendons and ligaments. Specifically, we aim to define the biochemical pathways that equip bone collagen to mineralize, cartilage to last a lifetime as the bearing surfaces of joints and tendons and ligaments to transmit or restrain high mechanical loads without failing. With this knowledge new targets for therapy and prevention of genetic and acquired human disorders of bones and joints are predicted.