RT info:eu-repo/semantics/doctoralThesis
T1 Sarcoplasmic reticulum Ca2+ dynamics in aging Drosophila and correlation with sarcopenia
A1 Río Lorenzo, Alba del
A2 Universidad de Valladolid. Facultad de Medicina
K1 Calcio
K1 Sarcopenia
K1 32 Ciencias Médicas
AB Aging still remains a mystery of biology and one of the most affected tissues inaging is skeletal muscle, whose loss of muscle mass and strength is calledsarcopenia. Age-dependent sarcopenia is not restricted to mammals, as it affectsother animal species including nematodes or flies. Cytosolic Ca2+ ion is theintracellular second messenger that triggers muscle contraction. The sarcoplasmicreticulum is the store of Ca2+ in the muscle cell, and it releases Ca2+ to the cytosolwhen muscle contracts. Sarcopenia has been linked to the loss of Ca2+homeostasis that trigger muscle contraction, but mechanistic details remainunsolved.Here we explore the hypothesis that an alteration of the Ca2+ content within thesarcoplasmic reticulum (SR) is at the origin of this loss of Ca2+ homeostasisobserved in sarcopenia. For investigating this hypothesis, we generated transgenicflies that express the ratiometric low affinity Ca2+ indicator GAP3 targeted to themuscle sarcoplasmic reticulum (erGAP3), and we developed a new method tocalibrate erGAP3 fluorescent signals into SR/ER Ca2+ concentrations ([Ca2+]SR/ER).With these tools we measured resting [Ca2+]SR in vivo along the fly life, and founda progressive decrease with aging that results in a tenfold reduction in the [Ca2+]SRin the oldest flies. Then, to explore the molecular mechanisms involved in thisdecrease of [Ca2+]SR we studied the expression levels of the main proteins involvedin [Ca2+]SR resting levels. In old muscle, we found a slight non-significant increasein the ryanodine receptors (RyR) and in the immunoglobulin protein (BiP)expression whereas the expression of the sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) decreased by 35%. Moreover, the loss of function of the skeletalmuscle was monitored by the well-characterized climbing assay, and found astrong correlation between the Ca2+ content of the sarcoplasmic reticulum and flyclimbing ability with aging. Furthermore, to assess whether the reduction of[Ca2+]SR content in the aged flies also affected the [Ca2+]C transients, we studiedthe cytosolic Ca2+ dynamics during muscle contraction in transgenic fliesexpressing the cytosolic Ca2+ sensor GCaMP in the muscle tissue. Thisexperiments showed that old flies released less Ca2+ to the cytosol in comparisonto young flies and, thus, these results validated those obtained in the SR.In order to investigate whether the reduction of SR Ca2+ content observed inmuscle was a universal phenomenon of aging that occurred also in other tissues we studied the progression of [Ca2+]ER in brain neurons and in the peripheralsensory wing neurons using the pan neuronal transgenic line, which expresseserGAP3 in all types of neurons. The [Ca2+]ER of the brain neurons did not changesignificantly with age, and remained stable along the whole fly life. However, thebehaviour is different in other neurons as we can also appreciate a decrease in the[Ca2+]ER of the sensory wing neurons, similar to what occurs in the skeletal muscle.Regarding the key molecular players, in contrast to the muscle, SERCA levelsremained unchanged in brain neurons whereas BiP and RyR levels are increasedin the aging brain.
YR 2020
FD 2020
LK http://uvadoc.uva.es/handle/10324/43643
UL http://uvadoc.uva.es/handle/10324/43643
LA eng
NO Departamento de Bioquímica y Biología Molecular y Fisiología
DS UVaDOC
RD 23-nov-2024