Shortstop recruits EB1/APC1 and promotes microtubule assembly at the muscle-tendon junction.
BACKGROUND
Shot (previously named Kakapo), is a Drosophila Plakin family member containing both Actin binding and microtubule binding domains. In Drosophila, it is required for a wide range of processes, including axon extension, dendrite formation, axonal terminal arborization at the neuromuscular junction, tendon cell development, and adhesion of wing epithelium.


RESULTS
To address how Shot exerts its activity at the molecular level, we investigated the molecular interactions of Shot with candidate proteins in mature larval tendon cells. We show that Shot colocalizes with EB1/APC1 and with a compact microtubule array extending between the muscle-tendon junction and the cuticle. Shot forms a protein complex with EB1 via its C-terminal EF-hands and GAS2-containing domains. In tendon cells with reduced Shot activity, EB1/APC1 dissociate from the muscle-tendon junction, and the microtubule array elongates. The resulting tendon cell, although associated with the muscle and the cuticle ends, loses its stress resistance and elongates.


CONCLUSIONS
Our results suggest that Shot mediates tendon stress resistance by the organization of a compact microtubule network at the muscle-tendon junction. This is achieved by Shot association with the cytoplasmic faces of the basal hemiadherens junction and with the EB1/APC1 complex.
Subramanian
Arul
A
Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel.
Prokop
Andreas
A
Yamamoto
Misato
M
Sugimura
Kaoru
K
Uemura
Tadashi
T
Betschinger
Joerg
J
Knoblich
Juergen A
JA
Volk
Talila
T
D000818:Animals; D015153:Blotting, Western; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D004330:Drosophila; D029721:Drosophila Proteins; D005455:Fluorescent Antibody Technique; D007365:Intercellular Junctions / Q000502:physiology; D007814:Larva / Q000502:physiology; D008840:Microfilament Proteins; D008870:Microtubules / Q000378:metabolism*; D009132:Muscles / Q000502:physiology; D011233:Precipitin Tests; D013710:Tendons / Q000254:growth & development*; D014162:Transfection
D003598:Cytoskeletal Proteins; D029721:Drosophila Proteins; D008840:Microfilament Proteins; C450828:shot protein, Drosophila