López, Rubén. Study of calcium sparks in skeletal and smooth muscle cells in normal and pathological conditions. 2016, PhD Thesis, University of Basel, Faculty of Science.
Available under License CC BY-NC (Attribution-NonCommercial).
Official URL: http://edoc.unibas.ch/diss/DissB_11744
As far as the mTOR is concerned, we found that in raptor knockout (RamKO) mice, the bulk of glycogen phosphorylase (GP) is mainly associated in its cAMP-non-stimulated form with sarcoplasmic reticulum (SR) membranes. In addition, radio ligand binding assay showed a ryanodine to dihydropyridine receptors (DHPRs) ratio of 0.79 and 1.35 for wild-type (WT) and raptor KO skeletal muscle membranes respectively, which was confirmed by Western Blot analysis. Peak amplitude and time to peak of the global calcium transients evoked by supramaximal ﬁeld stimulation were not different between WT and raptor KO. However, the increase in the voltage sensor-uncoupled RyRs leads to an increase of both frequency and mass of elementary calcium release events (ECRE) induced by hyper-osmotic shock in ﬂexor digitorum brevis (FDB) ﬁbres from raptor KO. These findings together with previous reports should be taken into consideration in the clinical practice when rapamycin or its analogs (rapalogs) is administrated to patients.
As far as RYR1–mutations in human patients and its relationship to bleeding abnormlities is concerned, 8/20 mutation carriers revealed abnormal bleeding scores compared with their healthy relatives (0/11). Similarly, MHS RYR1Y522S knock in mice exhibited 3 times longer bleeding times compared to their wild type littermates. The bleeding defect of MHS mice could be reversed by pre-treatment with the ryanodine receptor 1 antagonist dantrolene. Primary vascular SMCs from RYR1Y522S knock-in mice exhibited a higher frequency of subplasmalemmal Ca2+ sparks leading to a more negative resting membrane potential. Furthermore, Ca2+ sparks were blocked by pre-treatment with ryanodine or dantrolene. These results stimulated us to generate a model that could explain how impaired calcium homeostasis addressed by RyR1 mutation could affect bleeding without influencing platelet or coagulation factor function. Our results on impaired calcium homeostasis caused by RyR1 mutations could extend to other tissues that functionally express this channel.
In conclusion, the present study shows that the protein composition and function of the molecular machinery involved in skeletal muscle excitation–contraction (EC) coupling is affected by mTORC1 signaling and that RYR1 mutations cause prolonged bleeding by altering vascular SMC function and emphasize the potential therapeutic value of dantrolene in the treatment of such bleeding abnormalities.
|Advisors:||Pieters, Jean and Treves, Susan and Handschin, Christoph|
|Faculties and Departments:||05 Faculty of Science > Departement Biozentrum > Infection Biology > Biochemistry (Pieters)|
|Bibsysno:||Link to catalogue|
|Number of Pages:||1 Online-Ressource (X, 137 Seiten)|
|Last Modified:||20 Sep 2016 05:57|
|Deposited On:||20 Sep 2016 05:57|
Repository Staff Only: item control page