Mechano-transduction to muscle protein synthesis is modulated by FAK

Abstract

We examined the involvement of focal adhesion kinase (FAK) in mechano-regulated signalling to protein synthesis by combining muscle-targeted transgenesis with a physiological model for un- and reloading of hindlimbs. Transfections of mouse tibialis anterior muscle with a FAK expression construct increased FAK protein 1.6-fold versus empty transfection in the contralateral leg and elevated FAK concentration at the sarcolemma. Altered activation status of phosphotransfer enzymes and downstream translation factors showed that FAK overexpression was functionally important. FAK auto-phosphorylation on Y397 was enhanced between 1 and 6 h of reloading and preceded the activation of p70S6K after 24 h of reloading. Akt and translation initiation factors 4E-BP1 and 2A, which reside up- or downstream of p70S6K, respectively, showed no FAK-modulated regulation. The findings identify FAK as an upstream element of the mechano-sensory pathway of p70S6K activation whose Akt-independent regulation intervenes in control of muscle mass by mechanical stimuli in humans.

Costamere protein expression and tissue composition of rotator cuff muscle after tendon release in sheep

“…Muscle homogenates were prepared from cryosections of muscle biopsies as previously described 25. The protein homogenate (250 μg) was brought to a total volume of 750 μl with RIPA buffer.…”

A small scale cell culture system to analyze mechanobiology using reporter gene constructs and polyurethane dishes

“…Cell adhesion molecules like integrins, membrane associated receptors and strain sensitive channels have been described to transmit mechanical forces to intracellular structures like the actin cytoskeleton and second messengers like calcium flux (Asparuhova et al, 2009;Huveneers and Danen, 2009;Kiselyov and Patterson, 2009;Puklin-Faucher and Sheetz, 2009;Sharif-Naeini et al, 2010). Mechanobiochemical transformation in single cells is elicited by the stimulation of ERK1/2 kinase phosphorylation cascades, activation and nuclear translocation of transcription factors and modulation of gene expression (Khatiwala et al, 2009;Klossner et al, 2009;Liu et al, 2009;Rangaswami et al, 2009;Young et al, 2009).…”

Muscle-Targeted Gene Therapy of Charcot Marie-Tooth Disease is Dependent on Muscle Activity

“…Our previous findings in the suspension model show that reduced myogenic factor RNA expression after 24 hours of the reloading stimulus is related to a concomitant increase is the encoded protein (Fluck et al, 2008). This relates to the observation that FAK acts as a molecular switch for transition between anabolic and catabolic reactions in skeletal muscle and controls the protein synthetic pathway via p70S6K Klossner et al, 2009) . This suggests that transcript level changes in the early phase of reloading may reflect inverse alterations in protein synthesis.…”

“…FAK signals mechanical stimuli in muscle to gene expression and protein synthesis Klossner et al, 2009). We subjected the FAK-transfected soleus muscles to 7 days of hindlimb suspension and subsequent one day of reloading to assess the interaction of muscle activity with gene therapy.…”