Avian Synaptopodin 2 (Fesselin) Stabilizes Myosin Filaments and Actomyosin in the Presence of ATP

Abstract

Smooth muscle cells maintain filaments of actin and myosin in the presence of ATP although dephosphorylated myosin filaments and actin-myosin interactions are unstable under those conditions in vitro. Several proteins have been identified that stabilize myosin filaments and that stabilize actin-myosin interactions. Fesselin or synaptopodin 2 appears to be another such protein. Rapid kinetic measurements and electron microscopy demonstrated that fesselin, isolated from turkey gizzard muscle, reduced the rate of dissociation of myosin filaments. Addition of fesselin increased both the length and thickness of myosin filaments. The rate of detachment of myosin, but not HMM, from actin was also greatly reduced by fesselin. Data from this study suggest that fesselin stabilizes myosin filaments and tethers myosin to actin. These results support the view that one role of fesselin is to organize contractile units of myosin and actin.

Various Themes of Myosin Regulation

“…In contrast, the actin binding protein fesselin stabilizes smooth muscle myosin-2 filaments and increases filament length and thickness. Fesselin also decreases the rate of actomyosin dissociation in the presence of ATP and inhibits the actin-activation of the myosin ATPase activity in a concentration-dependent and tropomyosinindependent manner with an IC 50 of 0.6 µM [189, 190]. …”

Synaptopodin-2: a potential tumor suppressor

“…Synaptopodin-2 (SYNPO2), known as Myopodin or Fesselin, was first identified in chicken sand cysts in 1999. It has an isoelectric point (PI) of 9.3 and molecular weights of 79 kDa and 103 kDa [ 1 , 2 ]. In 2001, Lin et al documented a 54 kb minimal common deletion region on chromosome 4q25 of the genome associated with invasive prostate cancer [ 3 ].…”