Changes in myosin structure and function in response to glycation

Abstract

Nonenzymatic glycosylation (glycation) is recognized as an important post-translational modification underlying alterations of structure and function of extracellular proteins. The effect of glycation on intracellular proteins is, on the other hand, less well known despite the vital importance of intracellular proteins for cell, tissue, and organ function. The aim of this study was to explore the effects of glycation on the structure and function of skeletal muscle myosin. Myosin was incubated for up to 30 min with glucose and subsequently tested for structural and functional modifications by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry and a single-fiber in vitro motility assay, respectively. MALDI spectra revealed glycation-related structural alterations as evidenced by the disappearance of specific Lys-C proteolysis products and the appearance of higher mass peaks that are attributed to cross-linking by glucose. This change was paralleled by a significant reduction in the in vitro motility speed, suggesting a structure-related decline in myosin mechanics in response to glucose exposure. Further evidence that early glycation products form in the regulatory regions of the myosin molecule is derived from the fact that there is complete reversal of motility speed after reaction with the Schiff base-cleaving agent hydroxylamine hydrochloride. Thus, glycation of skeletal muscle myosin has a significant effect on both the structural and functional properties of the protein, a finding that is important in understanding the mechanisms underlying the impairment in muscle function associated with aging and diabetes.

Retinoic acid and sodium butyrate suppress the cardiac expression of hypertrophic markers and proinflammatory mediators in Npr1 gene-disrupted haplotype mice

“…The present results are consistent with the previous findings that RA exerts a beneficial effect in preventing cardiac remodeling, including the extracellular matrix (ECM), and fibrosis (9,10). Cardiac hypertrophy has been shown to be associated with increased expression of ␤-MHC and ␣-SKA (53,54). The present results suggest that an increased expression of hypertrophic marker genes such as ␤-MHC and ␣-SKA in the heart of Npr1 ϩ/Ϫ mice contributed to the development of cardiac hypertrophy in these animals.…”

Contributory Factors to Unsteadiness During Walking Up and Down Stairs in Patients With Diabetic Peripheral Neuropathy

“…It is likely that these changes are the result of physiological alterations to skeletal muscle before measureable sensory neuropathy is observed. Nonenzymatic glycation as a result of diabetes may affect the contractile machinery of skeletal muscle independently of neuropathy as shown previously on isolated animal muscle (27). This may at least party explain why changes have been observed proximally at the knee extensors as well as distally at the ankle extensors in diabetic patients without neuropathy.…”

Myofibrillar myosin ATPase activity in hindlimb muscles from young and aged rats

“…We favor the proposal that ADP release is the rate-limiting factor and may be altered with age because we have previously shown that during a maximal isometric contraction there is an increase in the apparent rate constant for myosin detachment from actin with age (Lowe et al, 2002), and ADP release is the critical step controlling detachment. Furthermore, it has been suggested that a structural alteration in the catalytic domain of MHC causes the age-related contractile deficits (Lowe et al, 2001;Lowe et al, 2002;Ramamurthy et al, 2001). A similar proposal has been suggested to explain sarcoplasmic reticulum Ca 2+ -ATPase functional alterations that occur with age (Chen et al, 1999;Ferrington et al, 1997).…”