Meeting Abstract

28.5  Wednesday, Jan. 5  Truncating the C-terminus of flightin disrupts flight muscle ultrastructure and reduces mechanical performance in Drosophila TANNER, B.C.W.*; MILLER, M.S.; MILLER, B.M.; LEKKAS, P.; IRVING, T.C.; MAUGHAN, D.W.; VIGOREAUX, J.O.; Univ. of Vermont, Burlington; Univ. of Vermont, Burlington; Univ. of Vermont, Burlington; Univ. of Vermont, Burlington; Illinois Institute of Technology, Chicago; Univ. of Vermont, Burlington; Univ. of Vermont, Burlington btanner@uvm.edu

In Drosophila flight muscle, flightin binds the myosin rod to maintain thick filament organization and sarcomere lattice integrity. Flightin has an amino acid sequence unique from any known protein domains and has no known homologues. To investigate C-terminal flightin contributions to muscle structure and function we created a transgenic Drosophila line (fln^ΔC44) that expresses a truncated flightin lacking the final 44 C-terminal amino acids. Despite nearly normal sarcomeric structure, fln^ΔC44 flies cannot beat their wings. X-ray diffraction measurement from resting, live flies revealed that the C-terminal flightin truncation slightly decreased myofilament lattice spacing, elevated disorder among thick and thin filaments, and repositioned myosin heads further from the thick filament backbone towards thin filaments, compared to a transgenic flightin-null rescued control line (fln⁺). Mechanical measurements from demembranated indirect flight muscle fibers showed no differences in net active and rigor tension between the two lines. However, small amplitude sinusoidal length perturbation analysis showed that fln^ΔC44 fibers produced approximately one third the oscillatory work and power as fln⁺. The frequencies of maximum work (123 vs. 154 Hz) and power (139 vs. 187 Hz) were also decreased for fln^ΔC44 compared to fln⁺, suggesting slower myosin cycling kinetics. These results demonstrate that the C-terminus of flightin is required for preserving lattice structure and for coordinating actomyosin cycling kinetics necessary to power flight.