Monoclonal antibody that inhibits biological activity of a mammalian ciliary neurotrophic factor

Retrograde axonal transport of signal transduction proteins in rat sciatic nerve

Neurons require a mechanism to transmit stable signals over the large distance from the nerve growth cone or terminal to the cell body, in order that information from the target tissue can be relayed to the cell body where it is required. Nerve growth factor (NGF), a target-derived neurotrophic factor, is thought to signal over this distance by receptor mediated internalization of NGF, followed by retrograde axonal transport of the NGF-receptor complex. In this paper we show, by immunohistochemistry of rat sciatic nerve, accumulation of phosphotyrosine immunoreactivity only on the distal side of a nerve crush, suggesting axonal transport of tyrosine kinases and/or tyrosine phosphorylated proteins primarily in a retrograde direction. Furthermore, we also show retrograde axonal transport of phosphoinositide 3-kinase, ERK, MEK and MEK kinase, of which all but MEK kinase are known to be activated downstream of tyrosine receptor kinase activation. The retrograde transport of these proteins suggests that they may be involved in transmission of signals along the axon, relaying neurotrophic factor receptor activation at the nerve terminal to the nerve cell body.

Production and characterization of monoclonal antibodies to human ciliary neurotrophic factor with defined epitope recognition

Ten mouse hybridoma lines producing monoclonal antibodies (Mabs) against recombinant human ciliary neurotrophic factor (rhCNTF) have been obtained. Two monoclonal antibodies belonging to the IgG1 class were selected and characterized. Their specificity was established by ELISA and Western blotting. Epitopes recognized by the two Mabs were investigated with ELISA and Western blotting by using rhCNTF mutants, rhCNTF fragments and synthetic peptides mimicking different portions of the CNTF molecule. The carboxy-terminal part of the CNTF and particularly the sequence between aa 150 and 159 appeared to constitute the immunodominant group. The fact that certain amino acid sequences of CNTF are conserved among species was utilized to examine the crossreactivity patterns of the two Mabs with rat sciatic nerve CNTF by Western blotting and immunohistochemistry. These antibodies will be useful for studying the distribution of CNTF in the nervous system and in developing an enzyme-linked immunosorbent assay for the quantitative determinations of CNTF in various neuropathologies.

Retrograde factors in peripheral nerves

The relationship between the neuron and its target is explored and the possible mechanisms for achieving correct connections are analysed. The most plausible mechanism is the presence of a retrograde intra-axonal message from the target to the neuronal cell body. The molecular form of the message and the mechanisms to achieve this signal transduction are discussed and it is proposed that there are two types of neurotrophic factors. One has a short-acting second messenger, itself incapable of surviving for the time required for transport to the cell body and thus requiring the transport of the message-generating complex to the cell body. The other has a long-lasting second messenger complex which is well able to survive the transport to the cell body so that there is no need for the transport of the neurotrophic factor itself. Thus all neurotrophic factors do not themselves require retrograde axonal transport and such non-transportable factors may generate intricate messages due to associations of signal transduction molecules via binding sites such as phosphorylated tyrosines and the src homology domain 2.

Retinoic acid potentiates the neurotrophic but not the mitogenic action of the class 1 heparin-binding growth factor (HBGF-1)

Retinoic acid promotes the neuronal survival properties of the class 1 heparin-binding growth factor (HBGF-1) on 8-day-old chick ciliary and sensory neurones. It has little or no effect on the survival promoting properties of class 2 heparin-binding growth factor (HBGF-2) on these cell types. Nerve growth factor (NGF) promoted survival of sympathetic and sensory neurones, and was unaffected at any concentration of retinoic acid. The mitogenic effect of both HBGF-1 and HBGF-2 was unaltered at any concentration of retinoic acid. It is suggested that naturally occurring gradients of retinoic acid, for example, as occur in the developing limb bud, could have a role in the development of normal innervation patterns through selective interaction with neurotrophic molecules.

Soluble and membrane-bound factors together account for target dependence of cultured parasympathetic neurons

The survival of avian ciliary ganglion (CG) neurons in culture depends upon an exogenous supply of trophic factor(s). Skeletal muscle, a normal ganglionic target tissue, is a well documented provider of survival-promoting activity, although the molecular basis for this ability to foster neuronal survival has not been thoroughly investigated. To identify the source of skeletal muscle support, dissociated neurons were plated into microwells containing either: a basal, trophically deficient medium; live pectoral muscle myotubes; medium conditioned by myotubes; membrane remnants of osmotically lysed myotubes; or, membrane remnants and conditioned medium. Neurons remaining in culture were counted after 1, 2, 5, and 7 days. The results reveal that neuronal survival is supported by both muscle conditioned medium and the membrane remnants of cultured myotubes. Each of these alone provides for only partial survival, while both combine to equal the activity of live myotubes. Treatment of the lysed membranes with either 1.5 M NaCl and/or 15 U heparin removed only 50-60% of the activity, suggesting that multiple factors are involved in the neuronal support obtained from lysed myotubes. This is in contrast to fibroblast remnants, which support some neuronal survival, but whose activity is wholly removed by NaCl. Conditioned medium also contains a heparin binding component which accounts for approximately 60% of its activity. These results indicate that full trophic support from the cultured target tissue requires at least two distinct active agents. The experiments further suggest that the target-derived factors responsible for neuronal survival in culture, and perhaps in vivo, are both soluble and membrane-associated molecules.