Specific proteolytic cleavage of agrin regulates maturation of the neuromuscular junction.
During the initial stage of neuromuscular junction (NMJ) formation, nerve-derived agrin cooperates with muscle-autonomous mechanisms in the organization and stabilization of a plaque-like postsynaptic specialization at the site of nerve-muscle contact. Subsequent NMJ maturation to the characteristic pretzel-like appearance requires extensive structural reorganization. We found that the progress of plaque-to-pretzel maturation is regulated by agrin. Excessive cleavage of agrin via transgenic overexpression of an agrin-cleaving protease, neurotrypsin, in motoneurons resulted in excessive reorganizational activity of the NMJs, leading to rapid dispersal of the synaptic specialization. By contrast, expression of cleavage-resistant agrin in motoneurons slowed down NMJ remodeling and delayed NMJ maturation. Neurotrypsin, which is the sole agrin-cleaving protease in the CNS, was excluded as the physiological agrin-cleaving protease at the NMJ, because NMJ maturation was normal in neurotrypsin-deficient mice. Together, our analyses characterize agrin cleavage at its proteolytic α- and β-sites by an as-yet-unspecified protease as a regulatory access for relieving the agrin-dependent constraint on endplate reorganization during NMJ maturation.
Bolliger
Marc F
MF
Department of Biochemistry, University of Zurich, 8057 Zurich, Switzerland.
Zurlinden
Andreas
A
Lüscher
Daniel
D
Bütikofer
Lukas
L
Shakhova
Olga
O
Francolini
Maura
M
Kozlov
Serguei V
SV
Cinelli
Paolo
P
Stephan
Alexander
A
Kistler
Andreas D
AD
Rülicke
Thomas
T
Pelczar
Pawel
P
Ledermann
Birgit
B
Fumagalli
Guido
G
Gloor
Sergio M
SM
Kunz
Beat
B
Sonderegger
Peter
P
D018171:Agrin / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D009046:Motor Neurons / Q000378:metabolism; D009412:Nerve Fibers / Q000378:metabolism; D009469:Neuromuscular Junction / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000096:biosynthesis / Q000378:metabolism*; D013116:Spinal Cord / Q000166:cytology; D009435:Synaptic Transmission / Q000502:physiology
D018171:Agrin; D012697:Serine Endopeptidases; C108493:neurotrypsin