Structure of laminin substrate modulates cellular signaling for neuritogenesis

Abstract

Increased neuritogenesis on the acidic matrix seemed to be associated with a higher degree of neuronal differentiation, since cell proliferation was immediately arrested upon plating, whereas on neutral matrices, the cell number increased six-fold within 24 hours. Investigation of the mechanisms mediating neurite outgrowth on each condition revealed that the extensive neuritogenesis observed on the acidic matrix involved activation of protein kinase A, whereas moderate neuritogenesis on neutral laminin was mediated by activation of protein kinase C and/or myosin light-chain kinase. Explants of cerebral cortex from P2 rats did not grow on the neutral laminin substrate but presented extensive cell migration and neurite outgrowth on the acidic laminin matrix. We propose that laminin can self-assemble independently of cell contact and that the assembling mode differentially modulates neuritogenesis and neuroplasticity.

Artificial Laminin Polymers Assembled in Acidic pH Mimic Basement Membrane Organization

“…Deposited on Coverslip-Although laminin aggregates could not be detected in neutral pH at 50 g/ml, we have previously demonstrated that deposits of the aggregated protein became visible when the laminin solution was incubated over the surface of a glass coverslip (11,14). Such deposits were characterized by immunostaining and shown to be morphologically different from others obtained in acidic pH.…”

“…When such explants were platted onto laminin adsorbed in neutral pH, laminin in EDTA, or poly-lysine, there was absolutely no migration or axonal growth. Immunolabeling of the matrices produced at each pH with anti-laminin antibodies revealed major morphological differences between them, whereas the acidic one seemed more flat and organized, which could account for its particular signaling properties to neural cells (11).…”

“…Artificial self-polymerization of laminin has been obtained in vitro either by maintaining the protein above a critical concentration (8) or by providing a surface of negative lipids to assist polymerization (9). More recently, we have found that diluting laminin in acidic pH led to instantaneous solution polymerization, whereas such polymers adsorbed on coverslips could induce neuritogenesis and cell migration out of explants of newborn rat brains (10,11). When such explants were platted onto laminin adsorbed in neutral pH, laminin in EDTA, or poly-lysine, there was absolutely no migration or axonal growth.…”

Biomaterials for spinal cord repair

“…As a major component of basement membrane ECM, laminin has frequently been shown to influence neurite outgrowth both in vitro [42][43][44][45] and in vivo [44,[46][47][48][49] . Laminin forms a sheetlike polymer that is best known for its critical involvement in basal membrane formation.…”

“…Laminin Laminin is a heterotrimeric glycoprotein consisting of α, β, and γ subunits that self-assemble in a temperature-, pH-and concentration-dependent manner [41,42] . As a major component of basement membrane ECM, laminin has frequently been shown to influence neurite outgrowth both in vitro [42][43][44][45] and in vivo [44,[46][47][48][49] .…”