Laminin is associated with the "neurite outgrowth-promoting factors" found in conditioned media.

Abstract

Conditioned media (CMs) from many cell types contain a factor that can adsorb to a polycationic substratum and cause neurons plated on that substratum to extend neurites rapidly and profusely. The extracellular matrix glycoprotein laminin, when bound to a substratum, elicits a similar response by neurons. In this report, six CMs that contain a "neurite outgrowth-promoting factor" were studied. Immunoprecipitation with affinity-purified anti-laminin antibodies demonstrated that laminin is present in all of them, and when it was selectively removed, there was a corresponding loss of neurite outgrowth-promoting activity in each CM. Antibodies to purified laminin failed, however, to block the outgrowth-promoting activity of five of the CMs tested, even though these antibodies blocked the outgrowth-promoting activity of purified laminin in the same assay. This result could reflect differences in amino acid sequence or protein modification between CM-derived laminin and the purified laminin used in generating antibodies. Alternatively, it could reflect the fact that other molecules bind to laminin in CMs and could interfere with the binding of antibodies to sites on lanmini that are important for biological activity.gators have prepared antisera directed against laminin that completely block neuronal responses to laminin-treated substrata (6, 10, 11). These sera have failed to affect the activities of most CM-treated substrata, suggesting that the active material in most CMs is not laminin. Recently, however, we have completed the purification of the neurite outgrowthpromoting factor present in bovine corneal endothelial (BCE) CM. In agreement with earlier results (4, 10, 13), we found that the active factor is an aggregate involving a heparan sulfate proteoglycan and two large proteins. One of these proteins has been identified as laminin. The other components can be separated from laminin and do not promote neurite outgrowth on their own. Details of the purification will be presented elsewhere.In this report, we present evidence that laminin is a component not only of the active factor in BCE-CM but also of the active factors in CMs produced by several other cell types. We suggest that laminin is responsible for the neurite outgrowth-promoting activity of all CMs with this activity. Reasons for the failure of anti-laminin antibodies to block the activity of many CM-treated substrata are discussed.The role of the extracellular matrix in influencing axon outgrowth has been the subject of several recent in vitro studies (1-6). Neurons of various types, when plated on extracellular matrix deposited by cultured cells, respond dramatically with neurite growth that commences quickly and progresses rapidly and extensively (4). This response occurs even in the absence of nerve growth factor or other appropriate survival factors (4, 7). A similar response is seen when neurons are plated on polycationic substrata that have been exposed to media conditioned by almost any cell type (1-4). This observation suggests that t...

Distribution and lateral mobility of voltage-dependent sodium channels in neurons [published erratum appears in J Cell Biol 1989 May;108(5):preceding 2001]

“…A similar situation may occur in innervated skeletal muscle where sarcolemmal channels appear immobile and congregated in patches (2,53). Moreover it has been shown that formation of basal lamina and the appearance of laminin is important in Schwann cell proliferation and for maturation of the axolemmal membrane (12,32).…”

A monoclonal antibody that blocks the activity of a neurite regeneration-promoting factor: studies on the binding site and its localization in vivo.

“…Polyclonal and monoclonal antibodies specific for laminin or for HeSPG selectively precipitate the INObearing complex harvested from media conditioned by the DRG cell line and by PC12 cells. Other investigators have also found that neurite-promoting factors released by a variety of cells in culture, including chick skeletal muscle (8), rat Schwannomas (16), and bovine corneal endothelial cells (28), consistently contain both laminin and HeSPG. INO binding is lost when the complex is dissociated and fractionated into its components; however, immunoreactivity can be recovered upon selective reassociation of two of these fractions.…”

“…In fact, several groups have provided convincing evidence that the outgrowth-promoting activity is associated with a HeSPG-laminin complex (16,28). To confirm that this was also true in the CM used in the present study, several monoclonal and polyclonal antibodies to laminin and HeSPG were tested for their ability to precipitate the INO determinant from the DRG cell line CM and PC12 cell CM (Table ID.…”

“…For instance, surfaces coated with laminin or fibronectin stimulate a much more rapid and extensive regeneration of neuronal processes than can serum-or collagen-coated plastic (2,4,9,24,29,31,39,44). The finding that laminin, in particular, provides an especially good substrate for outgrowth is of interest because a variety of non-neuronal cells secrete neurite regeneration-promoting factors (1,12,14,26), some of which are extracellular matrix complexes containing primarily laminin and heparan sulfate proteoglycan (HeSPG) (8,16,28).Since laminin is a component of a naturally occurring,1. Abbreviations used in this paper: CM, conditioned medium; CNS, central nervous system; DRG, dorsal root ganglion; HeSPG, heparan sulfate proteoglycan; PNS, peripheral nervous system.…”

Response of purified chick motoneurons to myotube conditioned medium: Laminin is essential for the substratum-binding, neurite outgrowth-promoting activity

“…An earlier characterization of the motoneuron NOPA from MCM indicated that it was similar in its mode of action, size, density and enzymatic susceptibilities to a 'neurite outgrowth-promoting factor' from bovine corneal endothelial cell conditioned medium (BCE-CM) [3,9]. It has recently been reported that immunoprecipiration of LA from BCE-CM, as well as several other types of conditioned media, eliminates the ability of these conditioned media to promote neurite outgrowth by rat sympathetic neurons [10]. In addition, purification of the active factor from BCE-CM has confirmed the presence of LA I!…”