A dual laminin/collagen receptor acts in peripheral nerve regeneration.

Abstract

A regeneration chamber was created in vivo by suturing a synthetic tube sealed at its distal end onto the proximal stump of a severed rat sciatic nerve. Nerves regenerated into tubes coated with laminin at a rate of 0.33 mm/day after a lag of about 2 days. At 25 days, regenerating nerves had extended 23% farther into laminin-coated tubes as compared with uncoated ones. Monoclonal antibody 3A3, which functionally interferes with a dual lanminin/collagen receptor, inhibited nerve regeneration into laminin-coated tubes by 32%. In contrast, monoclonal antibody JG22, which inhibits chicken matrix receptors, had no significant effect on regeneration. Immunohistochemical studies of teased adult rat sciatic nerves indicate that 3A3 bound to Schwann cells and possibly to axons. In other studies, the heterodimeric, laminin/collagen receptor recognized by 3A3 has been shown to be a member of the integrin superfamily of adhesive receptors. These data provide evidence that an integrin receptor functions in nerve regeneration in vivo.In adult mammals, damaged axons can regenerate for many centimeters within the peripheral nervous system. These regenerating axons are typically found within conduits of basement membranes, often in contact with Schwann cells (1, 2). Like many other basement membranes, those in the peripheral nervous system are comprised of laminin, collagen, fibronectin, and other extracellular matrix (ECM) components (3-7). In culture, purified fibronectin, collagen, and especially laminin stimulate outgrowth as well as guide nerve processes (8)(9)(10)(11)(12). This growth requires binding of cell-surface receptors to ECM adhesive proteins. Several ECM receptors and binding proteins have been identified, most notably a superfamily of heterodimeric proteins called integrins. Integrins are found in a wide variety of cell types where they mediate both cell-cell and cell-matrix adhesion (13-15). Of particular note are observations that integrins mediate neurite outgrowth in culture (16)(17)(18)(19).Prompted by recent studies implicating laminin in nerve regeneration in vivo (20, 21), we have sought to identify ECM receptors responsible for matrix-mediated nerve regeneration. To accomplish this, we have employed a method for isolating in vivo regenerating peripheral nerves within synthetic tubes (21-24). Peripheral nerves are severed, and their proximal stumps are capped with a tube sealed at its distal end (24) to form a chamber. The tubes are then filled with a solution containing monoclonal antibody (mAb) 3A3 (IgGl), which inhibits neurite outgrowth by PC12 cells (a rat pheochromocytoma cell line) on laminin and collagen culture substrata (25). It has been shown elsewhere (25) that mAb 3A3 binds to a heterodimeric receptor complex (185 kDa, 125 kDa) of the integrin superfamily. mAb 3A3 appears to recognize the a subunit of this laminin/collagen receptor, which can be immunoprecipitated from detergent extracts not only of PC12 cells but also of embryonic rat neural tissues (26). We show here that (i) lamin...

Extracellular Matrix Molecules And Their Receptors: Functions In Neural Development

“…In particular, β 1 -class integrins have been shown to mediate neuronal attachment and process outgrowth in response to several ECM proteins, including LN, FN, and several collagens. Of the eight known β 1 integrins (Table 1), five (α 1 , α 3 , α 5 , α 6 , α VN ) have been identified in either primary neurons or neuronal cell lines (Tomaselli et al 1988a, and unpublished, Turner et al 1989, Ignatius & Reichardt 1988, Ignatius et al 1990, Toyota et al 1990, Vogel et al 1990. Strong indirect evidence for the expression of α 4 by peripheral neurons comes from studies of their interactions with the alternatively spliced IIICS domain in fibronectin , Guan & Hynes 1990.…”

α4 Integrin Is Expressed during Peripheral Nerve Regeneration and Enhances Neurite Outgrowth

“…Antibody-blocking experiments suggest that these increased levels of FN contribute to the subsequent repair (Toyota et al, 1990;Wang et al, 1992;Bailey et al, 1993;Agius and Cochard, 1998). FN is expressed as different isoforms generated by alternative splicing of the primary gene transcript.…”

Characterization of neural cell adhesion sites: point contacts are the sites of interaction between integrins and the cytoskeleton in PC12 cells

“…For example, the ol5p 1 integrin is a fibronectin receptor that is highly expressed in developing and regenerating peripheral neurons (Lefcort et al, 1992), while the ~u6/31 integrin receptor is a laminin receptor, whose developmental regulation has been well characterized for retinal ganglion cells (Cohen et al, 1989). Other neurons are known to express ~vlpl and a3pl integrins as laminin/collagen receptors (Toyota et al, 1990;Reichardt and Tomaselli, 199 1;Tomaselli et al, 1993). Also, some neurons may express more than one class of laminin receptor, such as PC12 cells, which have al/31 and cr3pl receptors that are both functional (Tomaselli et al, 1990(Tomaselli et al, , 1993.…”