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      Impaired endocytosis of the ion channel TRPM4 is associated with human progressive familial heart block type I.

      The Journal of clinical investigation

      metabolism, Amino Acid Sequence, Amino Acid Substitution, Base Sequence, Bundle-Branch Block, genetics, physiopathology, Child, DNA, Electrocardiography, Endocytosis, Female, Genes, Dominant, Humans, Male, Middle Aged, Molecular Sequence Data, Mutation, Missense, Pedigree, Purkinje Fibers, RNA, Messenger, Sequence Homology, Amino Acid, Small Ubiquitin-Related Modifier Proteins, South Africa, TRPM Cation Channels

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          Abstract

          Progressive familial heart block type I (PFHBI) is a progressive cardiac bundle branch disease in the His-Purkinje system that exhibits autosomal-dominant inheritance. In 3 branches of a large South African Afrikaner pedigree with an autosomal-dominant form of PFHBI, we identified the mutation c.19G-->A in the transient receptor potential cation channel, subfamily M, member 4 gene (TRPM4) at chromosomal locus 19q13.3. This mutation predicted the amino acid substitution p.E7K in the TRPM4 amino terminus. TRPM4 encodes a Ca2+-activated nonselective cation (CAN) channel that belongs to the transient receptor potential melastatin ion channel family. Quantitative analysis of TRPM4 mRNA content in human cardiac tissue showed the highest expression level in Purkinje fibers. Cellular expression studies showed that the c.19G-->A missense mutation attenuated deSUMOylation of the TRPM4 channel. The resulting constitutive SUMOylation of the mutant TRPM4 channel impaired endocytosis and led to elevated TRPM4 channel density at the cell surface. Our data therefore revealed a gain-of-function mechanism underlying this type of familial heart block.

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          Author and article information

          Journal
          10.1172/JCI38292
          2735920
          19726882

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