Presence Of Nerve Growth Factor Receptors Research Articles

Preovulatory rise of NGF in ovine follicular fluid: possible involvement in the control of oocyte maturation.

Since nerve growth factor (NGF) is produced in vitro by granulosa cells after gonadotropin stimulation, the present research has been designed to investigate whether this neurotropin is involved in the events triggered by the gonadotropin surge that lead the follicle to ovulate a mature oocyte. To this aim, NGF levels in follicular fluid, collected before or 20 hours after the gonadotropin surge, was measured by ELISA. To evaluate whether NGF may have a non-neurotropic effect on follicle cells, the presence of NGF receptors was investigated by immunohistochemistry and further evaluated by analysing the tyrosine-phosphorylation pattern after NGF stimulation in vitro. The effect of NGF on the degree of cumulus expansion, cumulus-oocyte metabolic coupling, and meiotic maturation was finally studied by using the culture of follicle-enclosed oocyte. The results demonstrate that GnRH causes a dramatic rise of NGF in large follicles. Immunohistochemistry revealed a discrete positivity for trkA receptors localised in cumulus cells. Tyrosine phosphorylation pattern confirms that somatic cells are capable to transduce NGF signal. By contrast, all the oocytes examined were negative for trkA and did not change the phosphorylation pattern after NGF. In vitro NGF (100 ng/ml) induced a marked cumulus expansion and a progressive cumulus-oocyte uncoupling similar to that produced by gonadotropins. The addition of NGF also caused the resumption of meiosis in more than 70% of the oocytes analysed with an effect that is only slightly less pronounced than that of gonadotropins (80%). The increase in NGF secretion following gonadotropin surge suggests that this neurotropin may be involved in the control of oocyte maturation.

Nerve growth factor receptor-immunoreactive neurons within the developing human cortex.

A monoclonal antibody recognizing the p75 receptor for nerve growth factor (NGF) was used to assess the immunohistochemical expression of NGF receptors within the developing human neo-, limbic, and paralimbic cortices as well as the hippocampal complex. Between embryonic weeks 16 and 26, a transient population of neurons located within the upper and lower subplate zones of the neo-, limbic, and paralimbic cortices expressed the receptor for NGF. In contrast, NGF receptor-immunoreactive neurons were only observed in the upper subplate zone of the entorhinal cortex at embryonic week 40 (term), a staining pattern not observed in a 5-year-old specimen. The expression of NGF receptor-immunoreactive neurons within the upper subplate zone between embryonic weeks 16 and 40 was characterized by a dense band of immunoreactive neurons and neuropil. These neurons were bipolar with basal and apically directed neurites. NGF receptor-immunoreactive neurons were also scattered throughout the lower subplate zone and underlying white matter between embryonic weeks 19 and 26. These neurons were multipolar, with less apically directed neurites. NGF receptor-immunoreactive subplate neurons displayed a topographic distribution with the heaviest concentration found within limbic and paralimbic cortices as well as association neocortex. In contrast, light to moderate NGF receptor-immunoreactivity was seen in sensory-motor cortex. Within the hippocampal complex, only a few lightly stained NGF receptor-immunoreactive neurons were seen within the fimbria, hilar region of the dentate gyrus, and subiculum. The expression of NGF receptor-immunoreactivity increased within the subplate zone of the pre- and parasubiculum culminating in intense entorhinal cortex staining. As the entorhinal cortex merged with the developing inferior temporal association cortex, there was a marked reduction in staining intensity. In contrast to those in the subplate zone, neurons within the germinal zone and cortical plate were NGF receptor immunonegative at all times examined. The presence of NGF receptors in the subplate zone suggests that neurotrophins such as NGF play an important role in the transient viability of these neurons as well as in the guidance of cortical afferent inputs into topographically organized regions of the cerebral cortex.

Temporal pattern of nerve growth factor receptor expression in developing cochlear and vestibular ganglia in quail and mouse.

We have previously demonstrated the presence of specific receptors for nerve growth factor (NGF) in cochleovestibular ganglia of 72 h (stage 19-20) quail embryos, with a greater density of NGF receptors in the cochlear portion of the ganglion. The present study was conducted to determine the temporal pattern of NGF receptor expression in cochlear and vestibular ganglia throughout development, and was conducted in two species, quail and mouse. As in the quail, specific binding of 125I-NGF was detected in cochleovestibular ganglia of mouse embryos from an embryonic age equivalent to 72 h quail embryos (embryonic day 11, E11), with a similar concentration of 125I-NGF binding in the cochlear portion. Quantitative studies revealed that 125I-NGF binding continued to increase, in both cochlear and vestibular ganglia, for several days of development, and then began to decrease to minimal levels. Maximal levels were achieved at E7 in the quail, and E14 to E16 in the mouse, while minimal levels were reached by E13 in the quail, and E18 in the mouse. The level of 125I-NGF binding in cochlear ganglia was two to three times higher than in vestibular ganglia; a finding corroborated by radioautographic studies. In both quail and mouse, NGF receptors were more heavily concentrated in the ventromedial portion of the cochlear ganglion, adjacent to the cochlear duct; an area containing both support cells and peripheral neuronal processes. In the vestibular ganglion, 125I-NGF binding was more homogeneous, although small areas containing high densities of silver grains were observed. The presence of NGF receptors in cochlear and vestibular ganglia suggests that these ganglia may be responsive to and/or dependent upon NGF during their development.

Efficient Processing and Expression of Human Nerve Growth Factor Receptors in Xenopus laevis Oocytes: Effects on Maturation

The nerve growth factor (NGF) receptor is an integral membrane protein that is phosphorylated and heavily glycosylated. Determination of the amino acid sequence by molecular cloning indicates that the receptor is a cysteine-rich protein which contains a signal peptide sequence and spans the lipid bilayer with a single transmembrane sequence. A single mRNA of 3.8 kilobases was observed for the receptor, of which 1.5 kilobases is coding sequence. We have used microinjection of receptor RNA in Xenopus laevis oocytes to obtain cell surface expression of the receptor. The presence of NGF receptors in oocytes was verified by radioimmunoassay, specific binding of [125I]NGF, and metabolic labeling followed by immunoprecipitation. The NGF receptor protein was rapidly processed in oocytes and displayed extensive glycosylation. Furthermore, the presence of NGF receptors in oocytes potentiates the ability of progesterone to induce maturation.

Efficient processing and expression of human nerve growth factor receptors in Xenopus laevis oocytes: effects on maturation.

The nerve growth factor (NGF) receptor is an integral membrane protein that is phosphorylated and heavily glycosylated. Determination of the amino acid sequence by molecular cloning indicates that the receptor is a cysteine-rich protein which contains a signal peptide sequence and spans the lipid bilayer with a single transmembrane sequence. A single mRNA of 3.8 kilobases was observed for the receptor, of which 1.5 kilobases is coding sequence. We have used microinjection of receptor RNA in Xenopus laevis oocytes to obtain cell surface expression of the receptor. The presence of NGF receptors in oocytes was verified by radioimmunoassay, specific binding of [125I]NGF, and metabolic labeling followed by immunoprecipitation. The NGF receptor protein was rapidly processed in oocytes and displayed extensive glycosylation. Furthermore, the presence of NGF receptors in oocytes potentiates the ability of progesterone to induce maturation.

Human melanoma cells have both nerve growth factor and nerve growth factor-specific receptors on their cell surfaces.

Human melanoma cells were examined in an indirect membrane immunofluorescence assay for surface nerve growth factor (NGF) and NGF receptors. This assay revealed that human melanoma cells have various levels of NGF and NGF receptors on the plasma membrane, whereas a variety of human sarcoma and carcinoma tumor cells and normal human fibroblasts are negative. Surface NGF could be detected on melanoma cells with a rabbit antiserum directed to NGF at titers as high as 1:64; prior adsorption of this antibody with mouse 2.5S NGF resulted in a loss of fluorescence. The melanoma cells were positive whether or not they were grown in the presence of fetal calf serum. NGF production by human melanomas is a previously unrecognized property of this differentiated cell type. Although other cells in culture have been shown to produce NGF, the association of NGF production with the presence of NGF receptors on the cell surface is rare among tumor cells, and may represent an opportunity for "autostimulation" of melanoma cells by this growth factor.