Pikachurin: A Fibrous Protein Encoded by the EGFLAM Gene in Humans

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Pikachurin, also known as agrin-like protein (AGRINL) and EGF-like, fibronectin type-III and laminin G-like domain-containing protein (EGFLAM), is a fibrous protein that in humans is encoded by the EGFLAM gene. Pikachurin is a dystroglycan-interacting protein which has an essential role in the precise interactions between the photoreceptor ribbon synapse and the bipolar dendrites. The binding with dystroglycan (DG) depends on several factors (glycosylation of DG, presence of divalent cations, presence of other proteins). A non-correct binding between pikachurin and DG is associated with muscular dystrophies that often involve eye abnormalities. Discovery and nomenclature

Pikachurin is an extracellular matrix-like retinal protein first described in 2008 in Japan by Shigeru Sato et al., and named after Pikachu, a character of the Pokémon franchise. The name of this "nimble" protein was inspired due to Pikachu's "lightning-fast moves and shocking electric effects". Pikachurin was initially identified in a microarray analysis of gene expression profiles of the retinas of wild-type and Otx2 knockout mice. A RT-PCR analysis was used to confirm that Otx2 regulates the expression of pikachurin, it was known because there was an absence of expression of pikachurin in the Otx2 mice retina, so it indicates that Otx2 regulates pikachurin. The localization of pikachurin to synaptic cleft in the photoreceptor ribbon synapse was determined using fluorescent antibodies. Tissue targeting of gene disruption of pikachurin was used to determine that this protein is necessary for proper synaptic signal transmission and visual function. α-dystroglycan was shown to interact with pikachurin through immunoprecipitation. Pikachurin-dystroglycan interaction

Dystroglycan ligand with other proteins is essential. Glycosylation of dystroglycan is necessary for its ligand binding activity. Mutations in glycosyltransferase enzymes cause abnormal glycosylation of dystroglycan....
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