Muscle-specific calpain, p94, responsible for limb girdle muscular dystrophy type 2A, associates with connectin through IS2, a p94-specific sequence.
p94, a muscle-specific member of calpain family, is unique in that it undergoes rapid and exhaustive autolysis with a half-life of less than 1 h resulting in its disappearance from muscle. Recently, p94 was shown to be responsible for limb girdle muscular dystrophy type 2A. To elucidate the muscular proteolytic system mediated by p94 and to solve the mystery of its unusually rapid autolysis, we searched for p94-binding proteins by the two-hybrid system. Although calpain small subunit plays a crucial role for regulation of ubiquitous calpains, it did not associate with p94. After a screening of skeletal muscle library, connectin (or titin), a gigantic filamentous protein spanning the M- to Z-lines of muscle sarcomere, was found to bind to p94 through a p94-specific region, IS2. The connectin-insoluble fraction of washed myofibrils contained full-length intact p94, suggesting that connectin regulates p94 activity.
Department of Molecular Biology, Institute of Molecular and Cellular Biosciences, University of Tokyo, Japan.
H
H
Sorimachi
K
K
Kinbara
S
S
Kimura
M
M
Takahashi
S
S
Ishiura
N
N
Sasagawa
N
N
Sorimachi
H
H
Shimada
K
K
Tagawa
K
K
Maruyama
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002154:Calpain / Q000378:metabolism*; D002460:Cell Line; D064211:Connectin; D006801:Humans; D006868:Hydrolysis; D008565:Membrane Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism*; D009136:Muscular Dystrophies / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism*; D011817:Rabbits; D051381:Rats
D064211:Connectin; D008565:Membrane Proteins; D009124:Muscle Proteins; C577285:TTN protein, human; D011494:Protein Kinases; D002154:Calpain