| Autor: |
Trautmann G; Institute of Integrative Neuroanatomy, Neuromuscular Signaling and System, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Philippstrasse 12, 10115 Berlin, Germany.; Center of Space Medicine Berlin, 10115 Berlin, Germany., Block K; Institute of Integrative Neuroanatomy, Neuromuscular Signaling and System, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Philippstrasse 12, 10115 Berlin, Germany.; Center of Space Medicine Berlin, 10115 Berlin, Germany., Gutsmann M; Institute of Integrative Neuroanatomy, Neuromuscular Signaling and System, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Philippstrasse 12, 10115 Berlin, Germany., Besnard S; UR VERTEX 7480, CHU de Caen, Université de Caen Normandie, 10115 Caen, France., Furlan S; C.N.R. Institute of Neuroscience, 14000 Padova, Italy., Denise P; COMETE U1075, INSERM, CYCERON, CHU de Caen, Normandie Université, Université de Caen Normandie, 10115 Caen, France., Volpe P; Department of Biomedical Sciences, University of Padova, 14000 Padova, Italy., Blottner D; Institute of Integrative Neuroanatomy, Neuromuscular Signaling and System, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Philippstrasse 12, 10115 Berlin, Germany.; Center of Space Medicine Berlin, 10115 Berlin, Germany., Salanova M; Institute of Integrative Neuroanatomy, Neuromuscular Signaling and System, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Philippstrasse 12, 10115 Berlin, Germany.; Center of Space Medicine Berlin, 10115 Berlin, Germany. |
| Abstrakt: |
We investigated the shuttling of Homer protein isoforms identified in soluble (cytosolic) vs. insoluble (membrane-cytoskeletal) fraction and Homer protein-protein interaction/activation in the deep postural calf soleus ( SOL) and non-postural gastrocnemius ( GAS ) muscles of het -/- mice, i.e., mice with an autosomal recessive variant responsible for a vestibular disorder, in order to further elucidate a) the underlying mechanisms of disrupted vestibular system-derived modulation on skeletal muscle, and b) molecular signaling at respective neuromuscular synapses. Heterozygote mice muscles served as the control (CTR). An increase in Homer cross-linking capacity was present in the SOL muscle of het -/- mice as a compensatory mechanism for the altered vestibule system function. Indeed, in both fractions, different Homer immunoreactive bands were detectable, as were Homer monomers (~43-48 kDa), Homer dimers (~100 kDa), and several other Homer multimer bands (>150 kDA). The het -/- GAS particulate fraction showed no Homer dimers vs. SOL . The het -/- SOL soluble fraction showed a twofold increase (+117%, p ≤ 0.0004) in Homer dimers and multimers. Homer monomers were completely absent from the SOL independent of the animals studied, suggesting muscle-specific changes in Homer monomer vs. dimer expression in the postural SOL vs. the non-postural GAS muscles. A morphological assessment showed an increase (+14%, p ≤ 0.0001) in slow/type-I myofiber cross-sectional area in the SOL of het -/- vs. CTR mice. Homer subcellular immuno-localization at the neuromuscular junction (NMJ) showed an altered expression in the SOL of het -/- mice, whereas only not-significant changes were found for all Homer isoforms, as judged by RT-qPCR analysis. Thus, muscle-specific changes, myofiber properties, and neuromuscular signaling mechanisms share causal relationships, as highlighted by the variable subcellular Homer isoform expression at the instable NMJs of vestibular lesioned het -/- mice. |
