Myosin VI (MVI) is a unique unconventional motor moving backwards on actin filaments. In non-muscle cells, it is involved in cell migration, endocytosis and intracellular trafficking, actin cytoskeleton dynamics, and possibly in gene transcription. An important role for MVI in striated muscle functioning was suggested in a report showing that a point mutation (H236R) within the MVI gene was associated with cardiomyopathy (Mohiddin et al., J Med Genet 41:309–314, 2004). Here, we have addressed MVI function in striated muscle by examining its expression and distribution in rat hindlimb skeletal muscle. We found that MVI was present predominantly at the muscle fiber periphery, and it was also localized within muscle nuclei. Analysis of both the hindlimb and cardiac muscle longitudinal sections revealed ~3 μm striation pattern, corresponding to the sarcoplasmic reticulum. Moreover, MVI was detected in the sarcoplasmic reticulum fractions isolated from skeletal and cardiac muscle. The protein also localized to the postsynaptic region of the neuromuscular junction. In denervated muscle, the defined MVI distribution pattern was abolished and accompanied by significant increase in its amount in the muscle fibers. In addition, we have identified several novel potential MVI-binding partners, which seem to aid our observations that in striated muscle MVI could be involved in postsynaptic trafficking as well as in maintenance of and/or transport within the sarcoplasmic reticulum and non-sarcomeric cytoskeleton.Electronic supplementary materialThe online version of this article (doi:10.1007/s00418-012-1070-9) contains supplementary material, which is available to authorized users.

Matrix metalloproteinases (MMPs) are key regulators of extracellular matrix remodeling, but have also important intracellular targets. The purpose of this study was to examine the activity and subcellular localization of the gelatinases MMP-2 and MMP-9 in skeletal muscle of control and physically trained rats. In control hind limb muscle, the activity of the gelatinases was barely detectable. In contrast, after 5 days of intense exercise, in Soleus (Sol), but not Extensor digitorum longus (EDL) muscle, significant upregulation of gelatinolytic activity in myofibers was observed mainly in the nuclei, as assessed by high resolution in situ zymography. The nuclei of quiescent satellite cells did not contain the activity. Within the myonuclei, the gelatinolytic activity colocalized with an activated RNA Polymerase II. Also in Sol, but not in EDL, there were few foci of mononuclear cells with strongly positive cytoplasm, associated with apparent necrotic myofibers. These cells were identified as activated satellite cells/myoblasts. No extracellular gelatinase activity was observed. Gel zymography combined with subcellular fractionation revealed training-related upregulation of active MMP-2 in the nuclear fraction, and increase of active MMP-9 in the cytoplasmic fraction of Sol. Using RT-PCR, selective increase in MMP-9 mRNA was observed. We conclude that training activates nuclear MMP-2, and increases expression and activity of cytoplasmic MMP-9 in Sol, but not in EDL. Our results suggest that the gelatinases are involved in muscle adaptation to training, and that MMP-2 may play a novel role in myonuclear functions.Electronic supplementary materialThe online version of this article (doi:10.1007/s00418-012-0940-5) contains supplementary material, which is available to authorized users.

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Background / aims: The present study was initiated in order to investigate the protective effects of α-lipoic acid upon ethanol-induced DNA damage, lipid peroxidation and protein oxidation in the developing rat hippocampus and cerebellum. Methods: Pregnant Wistar rats received ethanol with, or without lipoic acid from gestation day (GD) 7 throughout lactation. The changes in DNA damage, protein carbonyl, lipid hydroperoxide, catalase and superoxide dismutase activities were measured in the hippocampus and cerebellum of male offspring at the end of the lactation period. Results: The results indicated that DNA damage, lipid peroxidation and protein oxidation in the hippocampus and cerebellum were significantly elevated in animals that received alcohol. However, the catalase and superoxide dismutase activity results showed patterns that differed from those of DNA damage, lipid peroxidation and protein oxidation. Lipoic acid treatment significantly decreased DNA damage compared with the group that were administered alcohol alone, and restored the elevated protein carbonyl and lipid hydroperoxide levels to the levels of the control group. Conclusions: Our findings confirm that oxidative stress and DNA damage occur in the developing hippocampus and cerebellum as a result of alcohol administration, and also suggest that lipoic acid has protective effects as an antioxidant against alcohol-induced disorders in the developing hippocampus and cerebellum.