Blockade of Metallothioneins 1 and 2 Increases Skeletal Muscle Mass and Strength.

Metallothioneins are proteins that are involved in intracellular zinc storage and transport. Their expression levels have been reported to be elevated in several settings of skeletal muscle atrophy. We therefore investigated the effect of metallothionein blockade on skeletal muscle anabolism in vitro and in vivo We found that concomitant abrogation of metallothioneins 1 and 2 results in activation of the Akt pathway and increases in myotube size, in type IIb fiber hypertrophy, and ultimately in muscle strength. Importantly, the beneficial effects of metallothionein blockade on muscle mass and function was also observed in the setting of glucocorticoid addition, which is a strong atrophy-inducing stimulus. Given the blockade of atrophy and the preservation of strength in atrophy-inducing settings, these results suggest that blockade of metallothioneins 1 and 2 constitutes a promising approach for the treatment of conditions which result in muscle atrophy.

Zinc binding to amyloid-beta: isothermal titration calorimetry and Zn competition experiments with Zn sensors.

Aggregation of the peptide amyloid-beta (Abeta) to amyloid plaques is a key event in Alzheimer's disease. According to the amyloid cascade hypothesis, Abeta aggregates are toxic to neurons via the production of reactive oxygen species and are hence directly involved in the cause of the disease. Zinc ions play an important role, because they are able to bind to Abeta and influence the aggregation properties. In the present work isothermal titration calorimetry and Zn sensors (zincon, Newport Green, and zinquin) were used to investigate the interaction of Zn with the full-length Abeta1-40 and Abeta1-42, as well as the truncated Abeta1-16 and Abeta1-28. The results suggest that Zn binding to Abeta induces a release of approximately 0.9 proton by the peptide. This correspond to the expected value upon Zn binding to the three histidines and indicates that further ligands are not deprotonated upon Zn binding. Such behavior is expected for carboxylates, but not the N-terminus. Moreover, the apparent dissociation constant (Kd,app) of Zn binding to all forms of Abeta is in the low micromolar range (1-20 microM) and rather independent of the aggregation state including soluble Abeta, Abeta fibrils, or Zn-induced Abeta aggregates. Finally, Zn in the soluble or aggregated Zn-Abeta form is well accessible for Zn chelators. The potential repercussions on metal chelation therapy are discussed.