Computational simulations suggest that the protein titin exerts a consistent mechanical force between 2 and 10 piconewtons per molecule in muscle fibers at their optimal length, and this force may...
Mechanism
Synthesis from 1 study
When your muscle is stretched just enough, a protein inside it called titin gets pulled slightly and turns on a signal that tells the cell to build more tools for making muscle proteins. Over time, this keeps your muscle at the right size without needing constant exercise.
Most probable mechanism
When muscle fibers are stretched just right, a spring-like protein inside them called titin gets pulled slightly, which turns on a molecular switch. This switch sends a signal that tells the cell to make more machines that build muscle proteins. Over time, more of these machines mean more muscle protein gets made, keeping the muscle at its ideal size.
Passive tension at optimal sarcomere length applies a mechanical force of 2–10 pN per titin molecule, inducing a conformational change in its kinase domain.
The open conformation of the titin kinase domain enables ATP-dependent phosphorylation and recruitment of signaling proteins such as nbr1.
The titin kinase-nbr1 complex activates serum response factor (SRF), initiating transcriptional programs that increase ribosome production.
Increased ribosome density overcomes steric hindrance within the myofilament lattice, enabling sustained synthesis of sarcomeric proteins including titin and actin.
Accumulation of sarcomeric proteins increases myofibrillar cross-sectional area, stabilizing muscle size at a homeostatic set point defined by titin tension.
Evidence from Studies
Supporting (1)
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Why exercise builds muscles: titin mechanosensing controls skeletal muscle growth under load
Contradicting (0)
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