Acetylcholine receptor expression in primary cultures of embryonic chick myotubes—I. Discoordinate regulation of α-, γ- and δ-subunit gene expression by calcitonin gene-related peptide and by muscle electrical activity

The level of acetylcholine receptor a-subunit mRNA in primary cultures ofchicken myotubes increases when the spontaneous electrical activity of the myotube is suppressed by the sodium channel blocker tetrodotoxin. This increase was prevented by two translational inhibitors: cycloheximide and anisomycin. Neither the basal level of a-subunit mRNA nor that of muscle-specific creatine phosphokinase mRNA was affected by these inhibitors. In contrast, cycloheximide potentiated the limited increase of a-subunit mRNA levels evoked by the neuropeptide calcitonin gene-related peptide. The high level of a-subunit mRNA elicited by tetrodotoxin treatment did not persist after subsequent addition of cycloheximide in the presence of tetrodotoxin, indicating that the continuous synthesis of protein factor(s) is necessary for this regulation. Moreover, cycloheximide decreased the high level of a-subunit mRNA present at early stages of in vitro maturation of muscle primary cultures without blocking the further increase of the muscle-specific creatine phosphokinase mRNA. Implications of the requirement for constant synthesis of protein factors on the induction of muscle-specific gene expression by blocking myotube electrical activity are discussed.

Section: Resultsmentioning

confidence: 99%

Induction of acetylcholine receptor alpha-subunit gene expression in chicken myotubes by blocking electrical activity requires ongoing protein synthesis.

Duclert

Piette

Changeux

1990

“…Denervation produced large the discussion in ref. 6 concerning the change in --subunit in thenmount of a-, -, v-, and 6-subunit mRNAs mRNA in mouse versus that in rat) and the chicken (11,12 stimulates AcChoR synthesis and subunit mRNA levels in chick myotubes (22,23), had no effect on any of the mouse subunit mRNAs. The lack of effect on E-subunit mRNA is in (33,34), and TTX-mimicked ARIA's effect in this regard.…”

mentioning

confidence: 98%

Acetylcholine receptor-inducing activity stimulates expression of the epsilon-subunit gene of the muscle acetylcholine receptor.

Martinou

Falls

Fischbach

et al. 1991

133

Motor neurons regulate the transcription of acetylcholine receptor subunit genes in postsynaptic muscle fibers both through muscle electrical activity produced by motor neuron acetylcholine release and by mechanisms independent of such transmitter release. Factors secreted by the motor neuron may mediate activity-independent regulation, including the postnatal switch from aj2fyS (embryonic type) to r2fiES (adult type) receptors. We have investigated the effect of putative trophic factors, agents affecting second-messenger systems, and muscle activity on the levels of acetylcholine receptor subunit mRNAs in primary mouse muscle cultures. We found that ARIA (acetylcholine receptor-inducing activity), a 42-kDa glycoprotein purified on the basis of its ability to increase the synthesis of acetylcholine receptors in chick myotubes, increases E-subunit mRNA levels up to 10-fold. In addition, ARIA stimulated a-, v-, and 6-subunit mRNA levels 2-fold but had no effect on the expression of the 8-subunit gene. These effects of ARIA were independent ofmuscle activity, and they were not mimicked by calcitonin gene-related peptide nor by thyroxine, forskolin, phorbol 12-myristate 13-acetate, the calcium ionophore A23187, basic fibroblast growth factor, or transforming growth factor B. Based on these data, we suggest that ARIA may act at the mammalian neuromuscular junction to induce adult-type acetylcholine receptors.

“…CGRP has a plethora of functions in the body. Aside from its vasodilatory and neuromodulatory actions, CGRP has been proposed to increase acetylcholine receptor synthesis at the neuromuscular junction (6) and to desensitize the acetylcholine receptor at the neuromuscular junction and the efferent synapses of the inner ear (5,7). CGRP-containing efferent fibers from the brainstem synapse at the inner ear end-organ sites, perhaps contributing to the processes responsible for the detection of auditory signals in the presence of background noise (8,9).…”

mentioning

confidence: 99%

Identification of a protein that confers calcitonin gene-related peptide responsiveness to oocytes by using a cystic fibrosis transmembrane conductance regulator assay.

Luebke

Dahl

Roos

et al. 1996

112