Disease relevance of MPP4

• Colocalization of MPP4 and autosomal recessive retinitis pigmentosa 26 (RP26) on chromosome 2q31-q33 makes this transcript an attractive candidate for the disease gene [1].

High impact information on MPP4

• MPP5 recruits MPP4 to the CRB1 complex in photoreceptors [2].
• RESULTS: A novel member of the scaffold connected to CRB1, called membrane palmitoylated protein (MPP) subfamily member 4 (MPP4), a membrane-associated guanylate kinase (MAGUK) protein, was identified [2].
• In this study, we show that MPP4 directly interacts with the Veli proteins via L27 heterodimerization in vitro [3].
• The MPP4 gene is localized to chromosome 2, in band 2q31-33, where a locus for autosomal recessive retinitis pigmentosa (RP26) has been mapped [4].
• Characterization of MPP4, a gene highly expressed in photoreceptor cells, and mutation analysis in retinitis pigmentosa [4].

Biological context of MPP4

• Alignment of the deduced amino acid sequence to sequence from protein databases revealed this gene, termed MPP4, to be a member of the membrane-associated guanylate kinase (MAGUK) protein family [1].
• Mutation analysis of the entire open reading frame of the MPP4 gene in a RP26 family revealed no pathologic mutations [4].

Anatomical context of MPP4

• CONCLUSIONS: These data imply that MPP4 and -5 have a role in photoreceptor polarity and, by association with CRB1, pinpoint the cognate genes as functional candidate genes for inherited retinopathies [2].
• MPP4 and MPP5 are closely related members of the p55-subfamily of membrane-associated guanylate kinases (MAGUKs) known to mediate the assembly of protein complexes at the plasma membrane of cell-cell junctions [3].
• While MPP4 is a component of the synaptic terminals of photoreceptors, MPP5 exclusively localizes to apical membrane domains of the outer limiting membrane (OLM) junctions [3].
• Due to the presence of only one PDZ motif, MPP4 is part of the p55 subfamily, named after the major palmitoylated erythrocyte membrane protein p55/MPP1 [1].

Analytical, diagnostic and therapeutic context of MPP4

• Immunofluorescence microscopy reveals extensive colocalization of Veli3 with both MPP4 and MPP5 [3].

References