The participation of a putative cell surface receptor for laminin and fibronectin in peripheral neurite extension

Abstract

We have used the CSAT (cell substrate attachment) monoclonal antibody (Mab), which is directed against a putative laminin and fibronectin receptor, to examine its role in the adhesive phenomena of neurons. This antibody was previously found to disturb the adhesion of several classes of fibroblasts and muscle. Here we report its effects upon neuronal-substrate adhesion. Two sources of neurons were investigated--the dorsal root and ciliary ganglia. Both responded similarly. Neurons plated in the presence of the CSAT Mab did not adhere to the substratum and process formation was inhibited completely for at least 24-48 hr. In explant cultures, when neurons were first allowed to extend processes prior to addition of the CSAT Mab, the results depended on the particular substrate. With some substrates, the neurites bundled and detached from the substratum; with others, they retracted and regrew to form large fascicles or bundles of processes. In dissociated cultures that already had extended processes, neurites fasciculated and cell bodies aggregated in response to the presence of the CSAT Mab. The magnitude of this response varied, depending upon the substrate. The antigen was localized, using immunofluorescence, on neuronal cell bodies, axons, and growth cones. This distribution correlated with its biological effects on all parts of the neuron. The antigen was isolated from neuronal cultures by immunoaffinity purification. It migrated in the molecular weight range of 140 kDa on reducing SDS-PAGE. This antigen is very similar to that isolated from fibroblasts, which is an integral membrane glycoprotein complex. The data presented implicate the participation of the CSAT antigen in neurite extension and fasciculation.

Cellular Strategies of Axonal Pathfinding

“…An example of an ECM protein that promotes outgrowth is the basement membrane component laminin. Axonal extension on laminin and most other ECM components requires that growth cones express appropriate receptors largely from the integrin family (Bozyczko and Horwitz 1986;Jessell 1988;Letourneau et al 1994;Huber et al 2003). Neurons have preferences for different ECM substrata according to the subtypes of integrin receptors they express (McKerracher et al 1996).…”

Structural requirements for the stimulation of neurite outgrowth by two variants of laminin and their inhibition by antibodies.

“…Although the cell surface molecules responsible for stimulating neurite outgrowth are currently only starting to be identified (see references 4,5,35), the well-characterized basement membrane protein laminin (26) has been shown to evoke many effects of extracellular matrices on neural cells: when used as a tissue culture substrate, laminin stimulates rapid neurite outgrowth (3), potentiates the survival-promoting activities of soluble neurotrophic factors (16), and can both induce an activation and increase the amount of the enzyme tyrosine hydroxylase in adrenal chromaffin cells (1). Laminin has also been shown to stimulate the division of Schwann cells (27).…”

Biomaterials for spinal cord repair

“…Fibronectin Fibronectin is a high molecular weight glycoprotein that binds to integrins and to other ECM proteins such as collagen [17,[55][56][57] . Soluble fibronectin circulates in the blood and is involved in clot formation, while insoluble fibronectin is found in the ECM.…”

“…Agnes E. Haggerty, et al Biomaterials for spinal cord repair 449 structure of the laminin polymer may be tied to its signaling capabilities. Certain structural configurations can induce regeneration and functional recovery when injected alone directly into the spinal cord following injury [49] .Fibronectin Fibronectin is a high molecular weight glycoprotein that binds to integrins and to other ECM proteins such as collagen [17,[55][56][57] . Soluble fibronectin circulates in the blood and is involved in clot formation, while insoluble fibronectin is found in the ECM.…”

“…Unlike some other ECM proteins, fibronectin does not undergo spontaneous polymerization, but rather does so via a highly-regulated, cell-mediated process [58] . The biological activity of fibronectin is mediated by RGD-integrin α5β1 binding, and also has an additional integrin-binding site [59] , PHRSN [60,61] , that results in a synergistic effect on cell adhesion and the activation of a variety of pathways leading to changes in >30 genes [59] .Although incapable of forming a hydrogel on its own, as a potential treatment strategy, it has been used in combination with hydrogels for spinal cord repair due to its cell-signaling properties through RGD-integrin binding [62] .After injury, it has been shown to elicit neurite outgrowth [57] .Fibronectin may be most relevant for regenerating damaged blood vessels via the α5β1 integrin receptor, which in turn could improve nutrient delivery to cells and reduce the infiltration of circulating macrophages following SCi [63] . Fibronectin has also been used in biosynthetic conduits for regeneration in a complete spinal transection model [64] .…”