Defective Saliva Secretion in Autoimmune NOD mice

描述(申请人提供)：干燥综合征(SjS)是一种自身免疫性疾病，主要针对唾液腺和泪腺，分别导致口干和眼睛干燥的症状。尽管最近有大量研究了解该病的发病机制，但目前尚不清楚SjS患者分泌功能障碍的确切机制。我们已经证明，针对M受体(M3R)的自身抗体能够通过将易患疾病的非肥胖性糖尿病(NOD)小鼠或人类原发SjS患者的纯化血清Ig G或F(ab‘)2片段转移到B细胞缺陷NOD.Igu缺失小鼠中而导致干燥。此外，我们还证明了NOD.IL-4 KO小鼠并没有丧失分泌功能，尽管除了缺乏lgG1抗M3R自身抗体外，所有与疾病相关的表型变化都没有发生，这表明lgG1同型功能是NOD小鼠分泌功能障碍的关键。因此，为了理解lgG1指导M3R的确切作用，我们假设lgG1的重要性不一定在其经典的恒定区效应功能的前提下，而是位于其可变区，其良好的特异性由lgG1亚型(可能是人类的lgG4)形成。在R21的应用中，我们建议研究三个特定的目标：特定的目标1：确定SjS的分泌丧失是否依赖于同型自身抗体，特别是lgG1抗鼠抗M3R自身抗体(人类的lgG4)。特异性目的2：研究同型抗体在分泌功能障碍中的作用是否由细胞内钙释放的改变而不依赖于抗鼠M3R自身抗体(人的lgG4)的恒定区而启动。具体目标3：确定通过结合lgG1抗鼠M3R自身抗体(在人类中为lgG4)与受体结合而改变的细胞内钙释放是否阻止水通道蛋白5移位到质膜，从而导致SjS分泌丧失。如果我们的假设被证明是正确的，SjS的研究将优先考虑M3R的表位图，以开发诊断和治疗策略，以恢复SjS患者的分泌能力。

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.