scholarly journals Involvement of ras p21 in neurotrophin-induced response of sensory, but not sympathetic neurons.

1993 ◽  
Vol 121 (3) ◽  
pp. 665-672 ◽  
Author(s):  
G D Borasio ◽  
A Markus ◽  
A Wittinghofer ◽  
Y A Barde ◽  
R Heumann
Keyword(s):  
Signal Transduction ◽  
Neurite Outgrowth ◽  
Neurotrophic Factors ◽  
Neurotrophic Factor ◽  
Sympathetic Neurons ◽  
Induced Response ◽  
Fab Fragments ◽  
Ras P21 ◽  
Ganglion Neurons ◽  
Embryonic Neurons

Little is known about the signal transduction mechanisms involved in the response to neurotrophins and other neurotrophic factors in neurons, beyond the activation of the tyrosine kinase activity of the neurotrophin receptors belonging to the trk family. We have previously shown that the introduction of the oncogene product ras p21 into the cytoplasm of chick embryonic neurons can reproduce the survival and neurite-outgrowth promoting effects of the neurotrophins nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), and of ciliary neurotrophic factor (CNTF). To assess the potential signal-transducing role of endogenous ras p21, we introduced function-blocking anti-ras antibodies or their Fab fragments into cultured chick embryonic neurons. The BDNF-induced neurite outgrowth in E12 nodose ganglion neurons was reduced to below control levels, and the NGF-induced survival of E9 dorsal root ganglion (DRG) neurons was inhibited in a specific and dose-dependent fashion. Both effects could be reversed by saturating the epitope-binding sites with biologically inactive ras p21 before microinjection. Surprisingly, ras p21 did not promote the survival of NGF-dependent E12 chick sympathetic neurons, and the NGF-induced survival in these cells was not inhibited by the Fab-fragments. The survival effect of CNTF on ras-responsive ciliary neurons could not be blocked by anti-ras Fab fragments. These results indicate an involvement of ras p21 in the signal transduction of neurotrophic factors in sensory, but not sympathetic or ciliary neurons, pointing to the existence of different signaling pathways not only in CNTF-responsive, but also in neurotrophin-responsive neuronal populations.

scholarly journals Role of PI 3-kinase, Akt and Bcl-2–related proteins in sustaining the survival of neurotrophic factor–independent adult sympathetic neurons

2001 ◽  
Vol 154 (5) ◽  
pp. 995-1006 ◽  
Author(s):  
Nina Orike ◽  
Gayle Middleton ◽  
Emma Borthwick ◽  
Vladimir Buchman ◽  
Timothy Cowen ◽  
...  
Keyword(s):  
Neurotrophic Factors ◽  
Molecular Mechanisms ◽  
Sympathetic Neurons ◽  
Dominant Negative ◽  
Downstream Effector ◽  
Cervical Ganglion ◽  
Negative Class ◽  
Natural Inhibitor ◽  
Ganglion Neurons ◽  
Related Proteins

By adulthood, sympathetic neurons have lost dependence on NGF and NT-3 and are able to survive in culture without added neurotrophic factors. To understand the molecular mechanisms that sustain adult neurons, we established low density, glial cell-free cultures of 12-wk rat superior cervical ganglion neurons and manipulated the function and/or expression of key proteins implicated in regulating cell survival. Pharmacological inhibition of PI 3-kinase with LY294002 or Wortmannin killed these neurons, as did dominant-negative Class IA PI 3-kinase, overexpression of Rukl (a natural inhibitor of Class IA PI 3-kinase), and dominant-negative Akt/PKB (a downstream effector of PI 3-kinase). Phospho-Akt was detectable in adult sympathetic neurons grown without neurotrophic factors and this was lost upon PI 3-kinase inhibition. The neurons died by a caspase-dependent mechanism after inhibition of PI 3-kinase, and were also killed by antisense Bcl-xL and antisense Bcl-2 or by overexpression of Bcl-xS, Bad, and Bax. These results demonstrate that PI 3-kinase/Akt signaling and the expression of antiapoptotic members of the Bcl-2 family are required to sustain the survival of adult sympathetic neurons.

Postnatal rat sympathetic neurons in culture. I. A comparison with embryonic neurons

1979 ◽  
Vol 42 (5) ◽  
pp. 1410-1425 ◽  
Author(s):  
E. Wakshull ◽  
M. I. Johnson ◽  
H. Burton
Keyword(s):  
Acetylcholine Receptors ◽  
Sympathetic Neurons ◽  
Gamma Aminobutyric Acid ◽  
Potential Amplitude ◽  
Cervical Ganglion ◽  
Dissociated Cell Culture ◽  
Ganglion Neurons ◽  
Embryonic Neurons

1. A morphological and physiological comparison was made between embryonically and postnatally derived superior cervical ganglion neurons (SCGN) grown in dissociated cell culture. It was found that while morphologically distinct, the physiological properties of the postnatal neurons were the same as their embryonic counterparts. 2. Intracellular injection of horseradish peroxidase (HPR) demonstrated that SCGN from any age of animal elaborated two basic types of processes, although the pattern of process ramification was unique for each neuron. The two types of proceses were 1) the large, smooth, rapidly tapering; and 2) the thin, nontapering variety, which often contained varicosities along its length. It is suggested that the former are dendritic in function, while the latter act as axons. 3. A difference was noted in somal size and the number of primary processes extended by the embryonic and postnatal neurons, with the latter more closely resembling the in vivo morphology. 4. Resting potentials and action-potential amplitudes of postnatal SCGN were comparable to those found previously for embryonic SCGN in vitro. 5. Iontophoretic application of putative neurotransmitter substances revealed the presence of acetylcholine receptors (AChR) on both embryonic and postnatal SCGN. Picrotoxin-sensitive depolarizing responses to iontophoresed gamma-aminobutyric acid (GABA) was seen on a few embryonic neurons, but not on the older cells. No responses were detected when norepinephrine (NE), glutamate, cAMP, substance P, or dopamine were applied to the SCGN of either age group. 6. Synatpic interaction between postnatal SCGN were found at an earlier in vitro age (12 days) than was the case for embryonic neurons (20 days). 7. Synaptic transmission was found to be chemical in nature. This was shown by 1) a dependence on external Ca2+ concentrations; 2) steplike fluctuations in synpatic potential amplitude, and 3) a variation in potential amplitude with changes in membrane potential. 8. It is concluded that the postnatal SCGN are able to survive in culture even when taken from animals up to 12.5 wk old. The elaboration of processes is in many ways strikingly similar to sympathetic neurons in the animal, and they are able to form functional synaptic interactions.

scholarly journals Cometin is a novel neurotrophic factor that promotes neurite outgrowth and neuroblast migration in vitro and supports survival of spiral ganglion neurons in vivo

2012 ◽  
Vol 233 (1) ◽  
pp. 172-181 ◽  
Author(s):  
Jesper Roland Jørgensen ◽  
Anette Fransson ◽  
Lone Fjord-Larsen ◽  
Lachlan H. Thompson ◽  
Jeffrey P. Houchins ◽  
...  
Keyword(s):  
Neurite Outgrowth ◽  
Neurotrophic Factor ◽  
Spiral Ganglion ◽  
Spiral Ganglion Neurons ◽  
Neuroblast Migration ◽  
Ganglion Neurons

scholarly journals EphA4 Obstructs Spinal Cord Neuron Regeneration by Promoting Excessive Activation of Astrocytes

2021 ◽  
Author(s):  
Xiaogang Chen ◽  
Lin Zhang ◽  
Fu Hua ◽  
Yu Zhuang ◽  
Huan Liu ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Growth Factor ◽  
Neurite Outgrowth ◽  
Neurotrophic Factors ◽  
Cellular Localization ◽  
Axon Regeneration ◽  
Chondroitin Sulphate ◽  
Cortical Cell ◽  
Inflammatory Factors ◽  
Cord Injury

AbstractStudies have found that molecular targets that regulate tissue development are also involved in regulating tissue regeneration. Erythropoietin-producing hepatocyte A4 (EphA4) not only plays a guiding role in neurite outgrowth during the development of the central nervous system (CNS) but also induces injured axon retraction and inhibits axon regeneration after spinal cord injury (SCI). EphA4 targets several ephrin ligands (including ephrin-A and ephrin-B) and is involved in cortical cell migration, axon guidance, synapse formation and astrocyte function. However, how EphA4 affects axon regeneration after SCI remains unclear. This study focuses on the effect and mechanism of EphA4-regulated astrocyte function in neuronal regeneration after SCI. Our research found that EphA4 expression increased significantly after SCI and peaked at 3 days post-injury; accordingly, we identified the cellular localization of EphA4 and ephrin-B ligands in neurons and astrocytes after SCI. EphA4 was mainly expressed on the surface of neurons, ephrin-B1 and ephrin-B3 were mainly localized on astrocytes, and ephrin-B2 was distributed on both neurons and astrocytes. To further elucidate the effect of EphA4 on astrocyte function after SCI, we detected the related cytokines secreted by astrocytes in vivo. We found that the levels of neurotrophic factors including nerve growth factor (NGF) and basic fibroblast growth factor (bFGF) increased significantly after SCI (NGF peaked at 3 days and bFGF peaked at 7 days); the expression of laminin and fibronectin increased gradually after SCI; the expression of inflammatory factors [interleukin (IL)-1β and IL-6] increased significantly from 4 h to 7 days after SCI; and the levels of glial fibrillary acidic protein (GFAP), a marker of astrocyte activation, and chondroitin sulphate proteoglycan (CSPG), the main component of glial scars, both peaked at 7 days after SCI. Using a damaged astrocyte model in vitro, we similarly found that the levels of related cytokines increased after injury. Consequently, we observed the effect of damaged astrocytes on neurite outgrowth and regeneration, and the results showed that damaged astrocytes hindered neurite outgrowth and regeneration; however, the inhibitory effect of injured astrocytes on neurite regeneration was reduced following ephrin-B receptor knockdown or inflammatory inhibition at 24 h after astrocyte injury. Our results showed that EphA4 regulates the secretion of neurotrophic factors, adhesion molecules, inflammatory factors and glial scar formation by binding with the ligand ephrin-B located on the surface of astrocytes. EphA4 affects neurite outgrowth and regeneration after SCI by regulating astrocyte function.

scholarly journals Watching Neurons Hand Off Molecules

2002 ◽  
Vol 10 (1) ◽  
pp. 3-34
Author(s):  
Stephen W. Carmichael
Keyword(s):  
Nerve Growth Factor ◽  
Growth Factor ◽  
Neurotrophic Factors ◽  
Neurotrophic Factor ◽  
Brain Derived Neurotrophic Factor ◽  
Target Cells ◽  
Nerve Growth ◽  
Hand Off ◽  
Presynaptic Neurons

Since the discovery of nerve growth factor, it has been thought that neurotrophic factors are released or secreted from target cells. However, more recently it has been suggested that a specific neurotrophic factor known as brain-derived neurotrophic factor (BDNF) may reach target cells directly from pre-synaptic axons. It has not been known how these molecules get from the neuron in which they are produced to the target cells. Keigo Kohara, Akihiko Kitamura, Mieko Morishima, and Tadaharu Tsumoto have demonstrated that BDNF is transported anterogradely from presynaptic neurons to target neurons.

Sign in / Sign up

Export Citation Format

Share Document