2026-04-27T01:41:03Zhttps://uvadoc.uva.es/oai/requestoai:uvadoc.uva.es:10324/436432021-06-23T13:47:17Zcom_10324_30605com_10324_894col_10324_41
UVaDOC
advisor
García-Sancho Martín, Francisco Javier
advisor
Alonso Alonso, María Teresa
author
Río Lorenzo, Alba del
editor
Universidad de Valladolid. Facultad de Medicina
2020-11-23T12:45:54Z
2020-11-23T12:45:54Z
2020
http://uvadoc.uva.es/handle/10324/43643
10.35376/10324/43643
Aging still remains a mystery of biology and one of the most affected tissues in
aging is skeletal muscle, whose loss of muscle mass and strength is called
sarcopenia. Age-dependent sarcopenia is not restricted to mammals, as it affects
other animal species including nematodes or flies. Cytosolic Ca2+ ion is the
intracellular second messenger that triggers muscle contraction. The sarcoplasmic
reticulum is the store of Ca2+ in the muscle cell, and it releases Ca2+ to the cytosol
when muscle contracts. Sarcopenia has been linked to the loss of Ca2+
homeostasis that trigger muscle contraction, but mechanistic details remain
unsolved.
Here we explore the hypothesis that an alteration of the Ca2+ content within the
sarcoplasmic reticulum (SR) is at the origin of this loss of Ca2+ homeostasis
observed in sarcopenia. For investigating this hypothesis, we generated transgenic
flies that express the ratiometric low affinity Ca2+ indicator GAP3 targeted to the
muscle sarcoplasmic reticulum (erGAP3), and we developed a new method to
calibrate 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 found
a progressive decrease with aging that results in a tenfold reduction in the [Ca2+]SR
in the oldest flies. Then, to explore the molecular mechanisms involved in this
decrease of [Ca2+]SR we studied the expression levels of the main proteins involved
in [Ca2+]SR resting levels. In old muscle, we found a slight non-significant increase
in 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 skeletal
muscle was monitored by the well-characterized climbing assay, and found a
strong correlation between the Ca2+ content of the sarcoplasmic reticulum and fly
climbing ability with aging. Furthermore, to assess whether the reduction of
[Ca2+]SR content in the aged flies also affected the [Ca2+]C transients, we studied
the cytosolic Ca2+ dynamics during muscle contraction in transgenic flies
expressing the cytosolic Ca2+ sensor GCaMP in the muscle tissue. This
experiments showed that old flies released less Ca2+ to the cytosol in comparison
to young flies and, thus, these results validated those obtained in the SR.
In order to investigate whether the reduction of SR Ca2+ content observed in
muscle 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 peripheral
sensory wing neurons using the pan neuronal transgenic line, which expresses
erGAP3 in all types of neurons. The [Ca2+]ER of the brain neurons did not change
significantly with age, and remained stable along the whole fly life. However, the
behaviour 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 levels
remained unchanged in brain neurons whereas BiP and RyR levels are increased
in the aging brain.
eng
Attribution-NonCommercial-NoDerivatives 4.0 Internacional
Calcio
Sarcopenia
Sarcoplasmic reticulum Ca2+ dynamics in aging Drosophila and correlation with sarcopenia
info:eu-repo/semantics/doctoralThesis
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