RAPSN

RAPSN
Identifiers
Aliases	RAPSN, RAPSYN, RNF205, CMS11, CMS4C, FADS, receptor associated protein of the synapse, FADS2
External IDs	OMIM: 601592; MGI: 99422; HomoloGene: 3708; GeneCards: RAPSN; OMA:RAPSN - orthologs
Gene location (Human) Chr. Chromosome 11 (human)[1] Band 11p11.2 Start 47,437,764 bp[1] End 47,449,143 bp[1]
Gene location (Mouse) Chr. Chromosome 2 (mouse)[2] Band 2 E1|2 50.44 cM Start 90,865,965 bp[2] End 90,876,074 bp[2]
RNA expression pattern Bgee Human Mouse (ortholog) Top expressed in muscle of thigh testicle gastrocnemius muscle Skeletal muscle tissue of rectus abdominis muscle of arm apex of heart biceps brachii deltoid muscle quadriceps femoris muscle glutes Top expressed in muscle tissue quadriceps femoris muscle skeletal muscle tissue muscle of thigh thoracic diaphragm heart secondary oocyte primary oocyte esophagus lens More reference expression data BioGPS More reference expression data
Gene ontology Molecular function acetylcholine receptor binding protein-membrane adaptor activity metal ion binding ionotropic glutamate receptor binding Cellular component cytoplasm cell junction neuromuscular junction Golgi apparatus postsynaptic membrane synapse cytoskeleton membrane centrosome cytosol plasma membrane postsynaptic specialization membrane Biological process positive regulation of neuromuscular synaptic transmission synaptic transmission, cholinergic positive regulation of neuron apoptotic process regulation of postsynaptic membrane organization chemical synaptic transmission establishment of protein localization to postsynaptic membrane Sources:Amigo / QuickGO
Orthologs Species Human Mouse Entrez 5913 19400 Ensembl ENSG00000165917 ENSMUSG00000002104 UniProt Q13702 P12672 RefSeq (mRNA) NM_005055 NM_032645 NM_009023 RefSeq (protein) NP_005046 NP_116034 NP_033049 Location (UCSC) Chr 11: 47.44 – 47.45 Mb Chr 2: 90.87 – 90.88 Mb PubMed search [3] [4]
Wikidata
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43 kDa receptor-associated protein of the synapse (rapsyn) is a protein that in humans is encoded by the RAPSN gene.^[5][6]

Function

This protein belongs to a family of proteins that are receptor associated proteins of the synapse. It contains a conserved cAMP-dependent protein kinase phosphorylation site. It is believed to play some role in anchoring or stabilizing the nicotinic acetylcholine receptor at synaptic sites. It may link the receptor to the underlying postsynaptic cytoskeleton, possibly by direct association with actin or spectrin. Two splice variants have been identified for this gene.^[6]

Role in health and disease

In the neuromuscular junction there is a vital pathway that maintains synaptic structure and results in the aggregation and localization of the acetylcholine receptor (AChR) on the postsynaptic folds. This pathway consists of agrin, muscle-specific tyrosine kinase (MuSK protein), AChRs and the AChR-clustering protein rapsyn, encoded by RAPSN. Genetic mutations of the proteins in the neuromuscular junction are associated with Congenital myasthenic syndrome (CMS). Postsynaptic defects are the most frequent cause of CMS and often result in abnormalities in the acetylcholine receptor. The vast majority of mutations causing CMS are found in the AChR subunits and rapsyn genes.^[7]

The rapsyn protein interacts directly with the AChRs and plays a vital role in agrin-induced clustering of the AChR. Without rapsyn, functional synapses cannot be created as the folds do not form properly. Patients with CMS-related mutations of the rapsyn protein typically are either homozygous for N88K or heterozygous for N88K and a second mutation. The major effect of the mutation N88K in rapsyn is to reduce the stability of AChR clusters. The second mutation can be a determining factor in the severity of the disease.^[7]

Studies have shown that most patients with CMS that have rapsyn mutations carry the common mutation N88K on at least one allele. However, research has revealed that there is a small population of patients who do not carry the N88K mutation on either of their alleles, but instead have different mutations of the RAPSN gene on both of their alleles. Two novel missense mutations that have been found are R164C and L283P and the result is a decrease in co-clustering of AChR with raspyn. A third mutation is the intronic base alteration IVS1-15C>A and it causes abnormal splicing of RAPSN RNA. These results show that diagnostic screening for CMS mutations of the RAPSN gene cannot be based exclusively on the detection of N88K mutations^[8] Interestingly, patients who bear the burden of CMS due to these rapsyn mutations often demonstrate a remarkable response to anticholinesterase drugs like pyridostigmine. Moreover, the supplemental inclusion of 3,4 DAP, ephedrine, or albuterol often yields significant clinical improvement.^[9]

Interactions

RAPSN has been shown to interact with KHDRBS1.^[10]

References

Further reading