This basic science study demonstrates that a specific 150-kDa titin fragment directly binds to and accelerates the polymerization of actin, a process regulated by phosphoinositides.
Does not yet inform clinical practice; extends in vitro evidence for titin-actin regulation but leaves relevance to human disease open.
Titin is a giant protein which extends from Z-line to M-line in striated muscles. We report here the purification of a 150-kDa titin fragment, obtained after V8 protease treatment of myofibrils. This polypeptide was located at the N1-line level, in a titin part known to exhibit stiff properties correlated to an association with actin. By solid or liquid phase binding assays and cosedimentation, we have clearly demonstrated a direct, saturable and relative high affinity binding of the native titin fragment to F-actin. The 150-kDa titin fragment was also shown to accelerate actin polymerization. Furthermore, the actin-titin interaction was found to be inhibited by phosphoinositides.
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Astier et al. (1998) studied this question.
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