Myosin phosphorylation potentiated steady state work output without altering contractile economy of mouse fast skeletal muscles

Abstract

Skeletal myosin light chain kinase (skMLCK)-catalyzed phosphorylation of the myosin regulatory light chain (RLC) increases (i.e. potentiates) mechanical work output of fast skeletal muscle. The influence of this event on contractile economy (i.e. energy cost/work performed) remains controversial, however. Our purpose was to quantify contractile economy of potentiated extensor digitorum longus (EDL) muscles from mouse skeletal muscles with (wild-type, WT) and without (skMLCK ablated, skMLCK) the ability to phosphorylate the RLC. Contractile economy was calculated as the ratio of total work performed to high-energy phosphate consumption (HEPC) during a period of repeated isovelocity contractions that followed a potentiating stimulus (PS). Consistent with genotype, the PS increased RLC phosphorylation measured during, before and after isovelocity contractions in WT but not in skMLCK muscles (i.e. 0.65 and 0.05 mol phosphate mol RLC, respectively). In addition, although the PS enhanced work during repeated isovelocity contractions in both genotypes, the increase was significantly greater in WT than in skMLCK muscles (1.51±0.03 versus 1.10±0.05, respectively; all data <0.05, =8). Interestingly, the HEPC determined during repeated isovelocity contractions was statistically similar between genotypes at 19.03±3.37 and 16.02±3.41 μmol P; respectively (<0.27). As a result, despite performing significantly more work, the contractile economy calculated for WT muscles was similar to that calculated for skMLCK muscles (i.e. 5.74±0.67 and 4.61±0.71 J kg μmol P, respectively (<0.27). In conclusion, our results support the notion that myosin RLC phosphorylation enhances dynamic contractile function of mouse fast skeletal muscle but does so without decreasing contractile economy.

Post‐activation potentiation induced by concentric contractions at three speeds in humans

“…From the perspective of the active state in a muscle the twitch is a submaximal response (vs. a tetanus) and potentiation is defined as the transient enhancement of both twitch peak torque and maximal rate of torque development (RTD) following a CC (Sale, 2002). This transient muscular facilitation can increase twitch torque upwards of ∼200% (Baudry & Duchateau, 2004; Smith et al., 2011) and following an isometric CC is maximal immediately and follows an exponential decay to baseline levels within ∼30 s to ∼10 min depending on the muscle and degree of PAP induced (Baudry & Duchateau, 2004; Gittings et al., 2018; Hamada et al., 2003; MacIntosh & Gardiner, 1987; MacIntosh et al., 2008; Seitz et al., 2015).…”

Studying Antifatigue Mechanism of Tyr-Pro-Leu-Pro in Exercise Mice Using Label-Free Proteomics

“…Importantly, H-YPLP upregulated the expressions of Acta1, triadin, Flnc, and Mylpf (Table ). Previous research has shown that the phosphorylation of the myosin regulatory light chain could enhance the dynamic contractile of the fast myofiber . Moreover, actin was downregulated by exercise fatigue in rat skeletal muscle .…”

“…Previous research has shown that the phosphorylation of the myosin regulatory light chain could enhance the dynamic contractile of the fast myofiber. 35 Moreover, actin was downregulated by exercise fatigue in rat skeletal muscle. 16 Lee et al 36 found the supplement of lignan-rich nutmeg extract upregulated the Acta1 expression in muscle tissue of aged mice.…”

Transcranial direct current stimulation of primary motor cortex modulates post-contraction potentiation

“…However, it is most effective after short (5 s)-duration contractile activity 8) . The proposed mechanisms under-*Correspondence: tomoyan0122@yahoo.co.jp lying post-activation potentiation are associated with phosphorylation of myosin regulatory light chains [9][10][11] and increased recruitment of higher-order motor units 12,13) . However, less is known about the involvement of the motor cortex in post-activation potentiation.…”