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活动能力，增加了对损伤的易感性。虚弱程度的增加不仅会影响个人的生活质量，还会给医疗保健系统带来额外的压力。由于这些原因和其他原因，对骨骼肌衰老过程的更深刻理解对于使美国人在以后的生活中保持健康至关重要。骨骼肌兴奋性的抑制已被确定为老年人力量下降的一个因素。在哺乳动物骨骼肌中，l型钙通道响应质膜的去极化，触发肌浆网（SR）释放钙，作为兴奋-收缩（EC）耦合的电压传感器。已经确定EC偶联受损会导致与年龄相关的肌肉无力。衰老肌肉中兴奋性的抑制（称为“EC解耦”）以SR - Ca释放减少为特征，这是质膜中l型通道数量减少的直接后果。RGK （Rad, Rem, Rem2, Gem/Kir）单体G蛋白家族的成员已被证明可以减少L型通道膜的表达，这提高了RGK蛋白介导骨骼肌可塑性变化最终导致EC解耦的可能性。因此，本提案的目的是研究RGK蛋白在与年龄相关的肌肉无力中的潜在作用。具体目标#1将寻求建立一个创新的模型系统来研究RGK蛋白在成人骨骼肌中的功能。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。该模型系统的有效性将通过膜片钳电生理和Ca成像进行评估。使用在Specific Aim #1中开发的方法，Specific Aim #2将探索RGK蛋白在有神经支配的肌肉中EC解偶联中的作用。特异性Aim #3将采用实时qRT-PCR和western blotting来确定老年小鼠中RGK蛋白表达是否增加。这项研究的发现可能会导致以RGK蛋白为靶点的药理学（甚至遗传学）治疗应用，从而减缓与年龄相关的肌肉无力的进展。此外，在本研究过程中收集的信息也可能有助于更好地理解与恶病质、糖尿病和退行性神经肌肉疾病相关的肌肉无力。

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.