Specific titin and myomesin domains stimulate myoblast proliferation

- Titin and myomesin as well as their domains stimulate myoblast proliferation.
- Ig-like and Fn type III domains activate proliferation via different pathways.
- IGF-1 autocrine signalling is partially involved in observed proliferative effects.

Myofibrillar proteins titin and myomesin stimulated myoblast proliferation as determined by MTT-test and labelled thymidine incorporation in the DNA. Specific Fn type III and Ig-like domains of these proteins were able to exert mitogenic effects as well. Proliferative effect of Fn type III domains was highly sensitive to inhibition of Ca2+/calmodulin dependent protein kinase, whereas the effect of Ig-like domains showed greater sensitivity to the inhibition of adenylyl cyclase - cAMP - PKA pathway. IGF-1 autocrine signalling inhibition partially suppressed mitogenic effects revealed by both domain types.