Defective Saliva Secretion in Autoimmune NOD mice

描述（由申请人提供）：干燥综合征（SjS）是一种自身免疫性疾病，主要靶向唾液腺和泪腺，分别导致口干和干眼症状。尽管最近有大量的研究来了解疾病的发病机制，分泌功能障碍的确切机制，在SjS是目前还没有。我们已经表明，靶向毒蕈碱3受体（M3 R）的自身抗体能够通过将来自易患病的非肥胖糖尿病（NOD）小鼠或人原发性SjS患者的纯化血清IgG或F（ab '）2片段转移到B细胞缺陷型NOD.Igu缺失小鼠中来诱导干燥。此外，我们证明了NOD.IL-4 KO小鼠除了缺乏IgG 1抗M3 R自身抗体外，尽管所有疾病相关的表型变化都没有失去分泌功能，这表明IgG 1同种型功能对NOD小鼠的分泌功能障碍至关重要。因此，为了理解IgGl指导M3 R的确切作用，我们认为IgGl的重要性不一定在其恒定区的经典效应子功能的前提下，而是在于其可变区，其精细特异性由IgGl同种型（推测为人类中的IgG 4）形成。在这项R21申请中，我们建议研究三个特定目的：特定目的1：确定SjS中的分泌丧失是否依赖于同种型自身抗体，特别是IgG 1抗小鼠抗M3 R自身抗体（人类中的IgG 4）。具体目标二：研究同种型抗体在分泌功能障碍中的作用是否由改变的细胞内钙释放启动，而不依赖于IgG 1抗小鼠M3 R自身抗体（人体中为IgG 4）的恒定区。具体目标3：确定IgG 1抗小鼠M3 R自身抗体（人体中为IgG 4）与受体结合后细胞内钙释放的改变是否阻断水通道蛋白5向质膜的转运，从而导致SjS分泌丧失。如果我们的假设被证明是正确的，SjS研究的优先事项将被赋予M3 R的表位定位的诊断和治疗策略，以恢复分泌能力的SjS患者的发展。

DESCRIPTION (provided by applicant): Sjogren's syndrome (SjS), an autoimmune disorder, targets mainly the salivary and lacrimal glands, resulting in dry mouth and dry eye symptom, respectively. Despite recent numerous studies to understand the disease pathogenesis, the exact mechanism for secretory dysfunction in SjS is not currently available. We have shown that autoantibodies targeting muscarinic 3 receptor (M3R) are capable of inducing dryness by transferring purified serum IgG or F(ab')2 fragments from disease-prone non-obese diabetic (NOD) mice or human primary SjS patients into the B-cell deficient NOD.Igu null mouse. Furthermore, we proved that the NOD.IL-4 KO mouse does not lose secretory function despite all disease-associated phenotypic changes except for the absence of lgG1anti-M3R autoantibodies, suggesting lgG1 isotypic function is critical to secretory dysfunction in the NOD mouse. Therefore, to understand the exact role of lgG1 directing M3R, we posit that the importance of lgG1 is not necessarily within the premise of its classical effector functions of constant region but resides in its variable region whose fine specificity is shaped by lgG1 isotype (presumably, lgG4 in humans). In this R21 application, we propose to investigate three Specific Aims: Specific Aim 1: Determine if loss of secretion in SjS is dependent on isotypic autoantibodies, especially lgG1 anti-mouse anti-M3R autoantibodies (lgG4 in humans). Specific Aim 2: To investigate if the effect of isotypic antibodies in secretory dysfunction is initiated by altered intracellular calcium release independent of constant region of lgG1 anti-mouse M3R autoantibodies (lgG4 in humans). Specific Aim 3: Determine if altered intracellular calcium release by binding of lgG1 anti-mouse M3R autoantibodies (lgG4 in humans) to the receptor blocks the translocation of aquaporin 5 to the plasma membrane, thus leading to loss of secretion in SjS. If our hypotheses are proven to be correct, the priority of SjS research will be given to the epitope mapping of M3R for the development of diagnostic and therapeutic strategies to restore secretory capacity in SjS patients.