Project Details
Description
Project Summary/Abstract
Sarcopenia is the progressive loss of skeletal muscle mass during aging and is a leading factor contributing to frailty,
debilitating injuries, loss of independence, and reduced quality of life in the elderly. Unfortunately, sarcopenia progresses
despite interventions such as increased physical activity and improved diet. During sarcopenia, the age-related decreases
in muscle strength result from a combination of loss of muscle mass (atrophy) and reduced muscle specific force (i.e.,
muscle force per unit of cross-sectional area). Increasingly, it is thought that it is the muscle weakness that accompanies
sarcopenia, rather than the loss of muscle size per se, as the principal contributor to disability. We recently found that
elements of contractile force generation in skeletal muscle are dependent on store-operated Ca2+ entry (SOCE) and that
this capacity is lost in aging skeletal muscle. This altered SOCE is directly associated with a reduced content of
mitsugumin 29 (MG29), a muscle-specific protein belonging to the synaptophysin (SYPL2) family which contains a
MARVEL domain involved in cholesterol binding, lipid handling and formation of oligomers of these proteins. MG29 is
essential for the proper formation of the transverse-tubule (TT) system and efficient SOCE. This leads to a link between
reduced MG29 expression in aged muscle and the development of muscle dysfunction in sarcopenia. Skeletal muscles
from young mg29-/- mice are similar to those from aged wild-type (WT) mice in that they demonstrate decreased specific
contractile force, reduced SOCE, reduced Ca release from the SR, reduced content of MG29, and altered TT morphology.
Therefore, our data demonstrate that key aspects of skeletal muscle aging are present in mg29-/- mice, making this model
applicable for this line of research. In this proposal we specifically hypothesize that MG29 is required for proper TT
formation and that SOCE functions in skeletal muscle through the action of specific protein domains. Decreased MG29
content in normal aged muscle leads to defective SOCE, which results in the decreased availability of Ca2+ for
contractility and age-related loss of muscle strength not accounted for by muscle atrophy. We will test this hypothesis
through two specific aims that will: a) examine the mechanistic basis for MG29 function in skeletal muscle, b) establish
how MG29 fits into the broader context of the multi-modal aspects of aging and E-C coupling, and c) provide
translational value for the treatment of sarcopenia. Aim 1 will elucidate the contribution of MG29 to SOCE, SR-Ca
release and contractility in aged skeletal muscle by using electroporation of MG29 cDNA or RNAi constructs to alter the
expression of MG29 and concomitantly evaluate SOCE function, SR-Ca release, contractile force and gene expression
levels. In Aim 2 we use a novel mouse model supported by molecular biology and biochemical approaches to resolve the
protein motifs responsible for the mechanism of MG29 function in lipid handling to establish the molecular mechanisms
of SOCE regulation by MG29 in skeletal muscle and how these mechanisms are altered in aging.
Status | Finished |
---|---|
Effective start/end date | 09/15/18 → 05/31/23 |
Funding
- National Institute on Aging: $510,119.00
- National Institute on Aging: $517,747.00
- National Institute on Aging: $539,210.00
- National Institute on Aging: $502,318.00
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