Calcium dynamics in caenorhabditis elegans pharynx

Résumé

The expression of the Ca2+ sensors cameleon YC2.1 and YC3.60 in C. elegans pharynx muscle cells allow measurement of calcium dynamics in these cells in vivo during long periods of pharyngeal activity, both in cytosol and mitochondria. 2.- Pharyngeal cytosolic calcium oscillations present variability, but it is possible to distinguish two types of cytosolic Ca2+ peaks: ü Square-wave peaks: prolonged elevations in [Ca2+], lasting for many seconds or even minutes. They are mostly present in young worms and disappear as the worm ages. ü Spikes: short peaks having widths smaller than 10s. They are maintained throughout the life of the worm. 3.- The pumping rate undergoes a progressive decline during aging due to sarcopenia. However, cytosolic spikes are present throughout the life of the worm. Therefore, there is a dissociation between calcium signalling and muscle contraction that develops with aging. 4.- The square-wave peaks are due to energy depletion in the pharynx cells. This energy depletion arrests Ca2+ pumps and precludes Ca2+ extrusion from the cytosol. Worms undergoing long square-wave peaks are therefore classified as energy-depleted. 5.- Square-wave peaks and energy-depleted worms appear more frequently in young worms, despite their larger energy content. This may be due to the very high energy use rate in young worms, which would overwhelm the energy production rate.