Coordinated effects of synaptic activity and muscle contraction on cpkc regulation by pdk1 and bdnf/trkb signalling. An approach towards the amyotrophic lateral sclerosis pathophysiology

Identifier:  TDX:2653

Handle: https://hdl.handle.net/20.500.11797/TDX2653

Authors:  Hurtado Caballero, Erica

Abstract:
The neuromuscular system is a complex and interconnected network in which presynaptic motoneurons and Schwann cells “tell” skeletal muscle to grow, to differentiate and how they should function. Conversely, skeletal muscle provides signals, including neurotrophins, that regulates the survival and function of motoneurons during development, maintenance and/or injury. Neurotrophins as BDNF, are regulated by activity and binding to TrkB triggers different pathways that impact on NMJ function, for example activating presynaptic PKCs. Thus, it is important to address how operates pre- and postsynaptic activities in physiological conditions to balance neuromuscular functionality through regulation of BDNF and PKC signalling. To address that, we stimulated the phrenic nerve of rat diaphragms with or without contraction to differentiate the effects of synaptic activity from that of muscle contraction. Then, we performed ELISA, Western Blot, qRT-PCR, immunofluorescence and electrophysiological techniques. Results showed that both synaptic activity and muscle contraction regulate cPKCβI maturation and activation in a complex and balanced way through PDK1 and BDNF/TrkB signalling. This regulation will determine NMJ functionality since our results also demonstrated that cPKCβI is directly involved in neurotransmission enhancing ACh release. However, what happens in a pathological context such us Amyotrophic lateral sclerosis (ALS) where neuromuscular activity is decreased? Could therapies as physical exercise, increasing activity, prevent the symptoms of ALS? To address that, we performed running and swimming-based training protocols to analyse the BDNF signalling in the plantaris muscle of SOD1-G93A mice by Western Blot. Results showed that in ALS disease where there is a loss of the connection between nerve and muscle, BDNF signalling is impaired but could be prevented in a different way depending on the nature and the intensity of the physical exercise imposed. Altogether, these results provide a mechanistic insight into the coordinated role of pre- and postsynaptic components to accurately preserve NMJ function.