Melanocortin receptors mediate α-MSH-induced stimulation of neurite outgrowth in neuro 2A cells

Abstract

Melanocortins (MC), neuropeptides derived from pro-opiomelanocortin, have been implicated in enhancing neurite outgrowth via an as yet unknown mechanism. Recently, five MC receptors have been identified, three of which, the MC3-R, the MC4-R and the MCs-R, are expressed in the nervous system. In this study, a-MSH and the melanocortin analog [D-PheT]ACTH (4-10) were able to stimulate neurite outgrowth in the neuroblastoma cell line Neuro 2A. ACTH (4-10), -/2-MSH and ORG2766 were inactive. In addition, the MCa-R antagonist [D-Arg8]ACTH (4-10), inhibited the a-MSH effect, indicating that the MCa-R mediated stimulation of neurite outgrowth by o~-MSH. Indeed, the presence of MCa-R mRNA in Neuro 2A cells was demonstrated by a RNase protection assay. Heterologous expression of the MCs-R in Neuro 2A cells lead to the recruitment of a responsiveness to -/2-MSH, but did not increase the effect of a-MSH on neurite outgrowth. This finding indicated that the function of MC4-R can also be exerted by another MC receptor, suggesting that the coupling to G,, which they have in common, plays an essential role in the neurite outgrowth promoting effect. This was further substantiated by the fact that forskolin treatment per se induced neurite outgrowth in a similar fashion. These data imply that the neurotrophic properties of a-MSH are likely to result from G~-coupled MC receptor activity in neuronal cells.

Targeting Melanocortin Receptors as a Novel Strategy to Control Inflammation

“…Histological and functional studies suggest that melanocortins do not enhance the rate of outgrowth, but they rather increase the number of newly formed sprouts at the site of lesion (Bar et al, 1993). More recent research suggests that neurotrophic effects induced by melanocortin are mediated by the MC4 receptor subtype (Adan et al, 1996). Indeed, ␣-MSH and [D-Phe 7 ]ACTH (4 -10) were shown to stimulate neurite outgrowth in the neuroblastoma cell line Neuro 2A that expressed the MC4R.…”

“…Indeed, ␣-MSH and [D-Phe 7 ]ACTH (4 -10) were shown to stimulate neurite outgrowth in the neuroblastoma cell line Neuro 2A that expressed the MC4R. Because the MC4R antagonist [D-Arg 8 ]ACTH (4 -10), inhibited such effect, it is likely that stimulation of neurite outgrowth by ␣-MSH was mediated by MC4R (Adan et al, 1996). Beneficial effects of ␣-MSH on clinical and neurophysiological recovery after experimental spinal cord injury were demonstrated in a weight drop model of traumatic spinal cord injury in rats (van de Meent et al, 1997).…”

Constitutive Traffic of Melanocortin-4 Receptor in Neuro2A Cells and Immortalized Hypothalamic Neurons

“…The cell distribution of MC4R has been mostly studied in HEK 293 cells that do not express endogenous MC4R. Neuroblastoma Neuro2A (N2A) cells originate from the neural crest (22), have been reported to express endogenous MC4R mRNA, and to respond to ␣-MSH by enhanced neurite extension (23). GT1-7 are immortalized hypothalamic neurons derived from transgenic mice expressing the SV40 T-antigen oncogene under the control of the gonadotropin-releasing hormone promoter (24 -26).…”

Interaction of Agouti protein with the melanocortin 1 receptor in vitro and in vivo

“…The interaction between Agouti protein and the Mc1r is likely to be representative of similar interactions that occur between additional melanocortin receptor subtypes and agouti-related molecules in the regulation of other biological processes (Adan et al 1996;Li et al 1996;Fan et al 1997;Huang et al 1997;Ollmann et al 1997;Shutter et al 1997). This possibility was first suggested by the phenotype of mice carrying the dominant Agouti allele lethal yellow (A y ) in which transcripts encoding normal Agouti protein are ubiquitously expressed (Miller et al 1993;Michaud et al 1994).…”