RGK proteins and aging muscle

描述(由申请人提供)：随着美国人预期寿命的增加，与年龄相关的肌肉无力成为一个日益严重的公共卫生问题。力量的下降限制了老年人的行动能力，增加了受伤的易感性。脆弱程度的增加不仅影响个人的生活质量，而且给卫生保健系统带来额外的压力。由于这些和其他原因，更深刻地了解骨骼肌的衰老过程对于使美国人在晚年保持健康至关重要。骨骼肌兴奋性的抑制已被认为是老年人力量减少的一个促成因素。在哺乳动物骨骼肌中，L型钙通道通过质膜去极化触发肌浆网(SR)钙释放，作为兴奋收缩(EC)偶联的电压传感器。已证实EC偶联受损会导致与年龄相关的肌肉无力。衰老肌肉兴奋性的这种抑制(称为“EC解偶联”)的特征是肌浆网钙释放减少，这是质膜上L类通道数量减少的直接结果。RGK(Rad，Rem，Rem2，Gem/Kir)等单体G蛋白家族的成员可以减少L型通道膜的表达，增加了RGK蛋白介导骨骼肌可塑性改变，最终导致EC解偶联的可能性。因此，这项建议的目的是调查RGK蛋白在年龄相关性肌肉无力中的潜在作用。具体目标#1将寻求建立一个研究成人骨骼肌中RGK蛋白功能的创新模型系统。为此，编码RGK蛋白的cDNA质粒将通过体内电穿孔传递到小鼠肌肉中。新模型系统的有效性将通过膜片钳电生理和钙成像进行评估。使用在特定目的#1中开发的方法，特定目的#2将探索RGK蛋白在去神经肌肉内皮细胞解偶联中的作用。具体目标#3将使用实时qRT-PCR和Western blotting来确定RGK蛋白在老年小鼠中的表达是否增加。这项研究的发现可能导致药物(甚至基因)靶向RGK蛋白将减缓与年龄相关的肌肉无力的进展的治疗应用。此外，在这项研究过程中收集的信息也可能有助于更好地了解与恶病质、糖尿病和退行性神经肌肉疾病相关的肌肉无力。 公共卫生相关性：与年龄相关的肌肉无力影响越来越多的美国人口的健康和日常活动。虽然骨骼肌兴奋性的抑制被认为是导致衰老肌肉力量不足的一个因素，但关于这种肌肉兴奋性的丧失是如何随着时间的推移而发展的，我们知之甚少。因此，这项研究提案的总体目标是提供有关老年人肌肉无力的分子机制的信息。

DESCRIPTION (provided by applicant): As life expectancy increases in the United States, age-related muscle weakness becomes a growing public health concern. Declines in strength limit mobility and increase susceptibility to injury in older individuals. Increased frailty not only impacts the quality of life of the individual but also places additional strain on the health care system. For these reasons and others, a more profound understanding of the aging process in skeletal muscle is critical for enabling Americans to remain healthy later in life. Depression of skeletal muscle excitability has been identified as a contributing factor to reduced strength in older individuals. In mammalian skeletal muscle, the L-type Ca channel serves as the voltage sensor for excitation-contraction (EC) coupling by triggering Ca release from the sarcoplasmic reticulum (SR) in response to depolarization of the plasma membrane. It has been established that impaired EC coupling contributes to age-related muscle weakness. This depression of excitability (termed "EC uncoupling") in aging muscle is characterized by a reduction in SR Ca release which is a direct consequence of a fewer number of L-type channels present in the plasma membrane. Members of the RGK (Rad, Rem, Rem2, Gem/Kir) family of monomeric G proteins have been demonstrated to reduce L- type channel membrane expression, raising the possibility that RGK proteins mediate plastic changes in skeletal muscle that ultimately result in EC uncoupling. Thus, the purpose of this proposal is to investigate a potential role for RGK proteins in age-related muscle weakness. Specific Aim #1 will seek to establish an innovative model system for the study of RGK protein function in adult skeletal muscle. To do so, cDNA plasmids encoding RGK proteins will be delivered to mouse muscle via in vivo electroporation. The validity of this new model system will be assessed with patch-clamp electrophysiology and Ca imaging. Using the methodology developed in Specific Aim #1, Specific Aim #2 will probe a role for RGK proteins in EC uncoupling in dennervated muscle. Specific Aim #3 will employ real-time qRT-PCR and western blotting to determine whether RGK protein expression is increased in older mice. The findings of this study may lead to therapeutic applications in which pharmacological (or even genetic) targeting RGK proteins would slow the progression of age-related muscle weakness. In addition, information gathered in the course of this study may also contribute to a better understanding of muscle weakness associated with cachexia, diabetes and degenerative neuromuscular disease. PUBLIC HEALTH RELEVANCE: Age-related muscle weakness impacts the health and daily activities of a growing segment of the American population. Although depression of skeletal muscle excitability has been identified as a contributing factor to strength deficits in aging muscle, little is known about how this loss of muscle excitability develops over time. Thus, the overall goal of this research proposal is to provide information about the molecular mechanisms that underlie muscle weakness in older individuals.