Subsynaptic Architecture Of The Nmj Laminins

The ECM is also clearly essential for establishing and maintaining the subsynaptic architecture of the NMJ. Details such as the alignment of presynaptic active zones with postsynaptic junctional folds and AChRs require trans-synaptic coordination of the molecular components of these complexes. Often this coordination will rely on cell-surface receptors, but it also requires an appropriate and precise subsynaptic organization of the ECM. There are many specialized components of the synaptic ECM, but the laminins are among the most interesting and have been well characterized for their role in synaptogenesis.

Figure 1.4. Laminin Protein Structure. Laminins are trimeric extracellular matrix molecules comprising an alpha chain, a beta chain, and a gamma chain. The total molecular weight of the trimers varies from 500 to 1000 kD. Alpha chains have N-terminal globular domains (domains IV and VI) separated by EGF-like repeats. This structure varies amongst the alphas, with a4 being truncated at its N-terminus and a5 being the longest, with additional EGF repeats present. The beta and gamma chains share this globular domain/EGF repeat structure at their N-termini. The central domain of the alpha chains and the C-terminal portion of the beta and gamma chains are coiled coil domains that are responsible for the assembly of the trimers. The alpha chains have an additional five globular domains (G domains) at their C-terminus. The laminins interact with many other ECM proteins. The N-terminal and C-terminal globular domains of the alpha chain both mediate interactions with integrins and heparin. Dystroglycan also binds the C-terminal G domains of the alpha chains. The chain mediates interactions with nidogen/entactin and agrin.

Figure 1.4. Laminin Protein Structure. Laminins are trimeric extracellular matrix molecules comprising an alpha chain, a beta chain, and a gamma chain. The total molecular weight of the trimers varies from 500 to 1000 kD. Alpha chains have N-terminal globular domains (domains IV and VI) separated by EGF-like repeats. This structure varies amongst the alphas, with a4 being truncated at its N-terminus and a5 being the longest, with additional EGF repeats present. The beta and gamma chains share this globular domain/EGF repeat structure at their N-termini. The central domain of the alpha chains and the C-terminal portion of the beta and gamma chains are coiled coil domains that are responsible for the assembly of the trimers. The alpha chains have an additional five globular domains (G domains) at their C-terminus. The laminins interact with many other ECM proteins. The N-terminal and C-terminal globular domains of the alpha chain both mediate interactions with integrins and heparin. Dystroglycan also binds the C-terminal G domains of the alpha chains. The chain mediates interactions with nidogen/entactin and agrin.

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