Targeting of glycine receptor subunits to gephyrin-rich domains in transfected human embryonic kidney cells. rapsyn remained intracellular, whereas rapsyn-induced clusters of muscle mass AChRs reached the cell surface. Additional studies exposed a second rapsyn RNA varieties in SCG generated by alternate splicing and proficient to encode a novel short rapsyn isoform. However, this isoform clustered neither neuronal nor muscle mass AChRs in heterologous cells. Most telling, the number, size, and denseness of AChR clusters Celecoxib in SCG did not differ significantly between neonatal mice bearing a targeted mutation of the rapsyn gene and littermate settings. Thus, rapsyn is definitely dispensable for clustering of ganglionic neuronal nicotinic AChRs. electric organ (Sobel et al., 1977; Neubig et al., 1979). Rapsyn is also codistributed with AChRs in the neuromuscular junction; rapsyn and AChRs appear together at the earliest phases of synaptogenesis and are present at 1:1 stoichiometry at adult synapses (Froehner et al., 1981; LaRochelle and Froehner, 1986; Noakes et al., 1993). That rapsyn is sufficient to cluster AChRs was demonstrated by coexpression of recombinant protein in nonmuscle cells: AChRs are diffusely distributed when indicated on their own but become aggregated into high-density clusters when coexpressed with rapsyn (Froehner et al., 1990; Phillips et al., 1991a). That rapsyn is necessary for synaptogenesis was demonstrated genetically in mice: no AChR clusters form at neuromuscular junctions of mice bearing a targeted mutation of the rapsyn gene, and homozygous mutants pass away of respiratory failure within a few hours of birth (Gautam et al., 1995). To day, no info is definitely available on the mechanisms that induce clustering of nicotinic AChRs at interneuronal synapses. We have carried out to address this problem at the relatively accessible synapse created by autonomic preganglionic axons on sympathetic neurons in the superior cervical ganglion (SCG) of the mouse. Because neuronal and muscle mass nicotinic AChR subunits are related in primary sequence (Lindstrom, 1996), we began by testing the possibility that rapsyn might play a crucial part in neurons as it does in muscle mass. We show here that sympathetic neurons communicate RNAs encoding both full-length rapsyn and a novel shorter isoform generated by alternate splicing. Moreover, rapsyn can induce aggregation of neuronal AChRs coexpressed in heterologous cells. However, three lines of evidence indicate that rapsyn is not a critical mediator of Rabbit Polyclonal to SREBP-1 (phospho-Ser439) AChR clustering at ganglionic synapses. First, rapsyn protein is definitely undetectable at AChR clusters in the SCG. Second, although rapsyn created clusters with both muscle mass and neuronal AChRs in heterologous cells, only the former were transported to the plasma membrane. Celecoxib Third, and most telling, both synaptic and nonsynaptic AChR clusters created in SCGs of rapsyn-deficient mutant mice. MATERIALS AND METHODS Sympathetic ganglia, skeletal muscles, and brains were dissected from timed embryonic or postnatal mice. Mice bearing a targeted mutation of the rapsyn gene have been explained previously (Gautam et al. 1995) and were taken care of on a Celecoxib 129SV C57BL6 cross background. Homozygous mutants were readily recognized because they died within a few hours of birth, but their genotype was confirmed by PCR. Littermates of the rapsyn mutants or wild-type C57BL6 (The Jackson Laboratory, Bar Harbor, ME) or ICR mice (Harlan Sprague Dawley, Indianapolis, IN) were used as settings. Four rat monoclonal antibodies to AChR subunits were from Jon Lindstrom (University or college of Pennsylvania) and from your Developmental Studies Hybridoma Standard bank (Iowa City, IA). Monoclonal antibody (mAb) 35 recognizes mouse AChR (1) subunit; mAb 210 recognizes mouse AChR 1 and 5 subunits; mAb 299 recognizes mouse AChR 4 subunit; and mAb 270 recognizes mouse AChR 2 subunit (Lindstrom, 1996). Two additional mouse monoclonal antibodies against subunits (mAb 398 and mAb 399; Chemicon, Temecula, CA) and a polyclonal antibody to 3 subunit (AChR 3; Santa Cruz Biotechnology, Santa Cruz, CA) were also tested but did not detectably stain SCG. Monoclonal antibody to the synaptic vesicle protein SV2 was a gift from Kathleen Buckley (Harvard Medical School, Boston, MA) (Buckley and Kelly, 1985). mAb 7a to gephyrin was a gift from Heinrich Betz (Max-Planck-Institute for Mind Study) (Kirsch and Betz, 1993). Affinity-purified rabbit anti-rapsyn polyclonal antibody 5943 and mouse anti-rapsyn mAb 1234 were explained previously (Phillips et al., 1991b). Rabbit antibodies to mouse laminin 1 and rat neural cell adhesion molecule (NCAM) were generated in our laboratory. Secondary antibodies included FITC-goat anti-rat (Organon Teknika-Cappel, Western Chester, PA), Cy3-goat anti-rat and.