Nerve-induced disruption and reformation of beta1-integrin aggregates during development of the neuromuscular junction.
The earliest biochemical change detected during synaptogenesis is a local elimination of muscle basal lamina proteins. To explore whether this provides signal(s) that regulate postsynaptic differentiation, we examined the effects of innervation on the distribution of beta1-integrins, which were initially present in scattered aggregates complexed with basal lamina ligands. These beta1-integrin aggregates disappear along paths of nerve contact as their basal lamina ligands are eliminated. New accumulations of these proteins then form during assembly of the postsynaptic apparatus. The new beta1-integrin aggregates at developing synapses form partly via a redistribution of mobile molecules on muscle surface. We thus consider whether (a) the removal of integrins' basal lamina ligands alters their cytoplasmic ligand-interactions, causing the dissociation of integrin clusters, and (b) this receptor modulation helps to transduce local changes in pericellular protease activity into cytoplasmic signals that control postsynaptic differentiation.
Anderson
M J
MJ
Department of Anatomy, The University of Calgary, Alberta, Canada. mjanders@acs.ucalgary.ca
Shi
Z Q
ZQ
Zackson
S L
SL
D000818:Animals; D002454:Cell Differentiation; D019812:Heparan Sulfate Proteoglycans / Q000378:metabolism; D019012:Integrin beta1 / Q000378:metabolism*; D007797:Laminin / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D009469:Neuromuscular Junction / Q000196:embryology / Q000378:metabolism*; D011950:Receptors, Cholinergic / Q000378:metabolism; D013569:Synapses / Q000378:metabolism; D014982:Xenopus laevis / Q000196:embryology
D019812:Heparan Sulfate Proteoglycans; D019012:Integrin beta1; D007797:Laminin; D011950:Receptors, Cholinergic