RAPSN

43 kDa receptor-associated protein of the synapse (rapsyn) is a is_associated_with::protein that in humans is encoded by the RAPSN is_associated_with::gene.

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

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 is_associated_with::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 is_associated_with::RNA. These results show that diagnostic screening for CMS mutations of the RAPSN gene cannot be based exclusively on the detection of N88K mutations

Interactions
RAPSN has been shown to interact with is_associated_with::KHDRBS1.