Characterization of the tyrosine phosphorylation and distribution of dystrobrevin isoforms.
Dystrobrevin, a member of the dystrophin family of proteins, was initially identified as a major tyrosine phosphorylated synaptic protein in the electric organ of Torpedo californica. In this paper, we show that the major sites of tyrosine phosphorylation of Torpedo dystrobrevin are within its C-terminus, on Tyr-693 and Tyr-710. Cloning of the mammalian homologue of dystrobrevin has recently shown that this phosphotyrosine containing tail, or PYCT, is subject to alternative splicing. To compare the expression and distribution of PYCT- and PYCT+ splice variants, we generated antibodies against different regions of dystrobrevin. Here we show that the PYCT- isoform of 62 kDa is expressed at high levels in all tissues examined. In contrast, PYCT+ isoforms are expressed primarily in brain and muscle, where they are concentrated at synapses. Moreover, PYCT+ isoforms associate more tightly with the membrane and with syntrophin, another synaptically enriched protein. These results suggest that PYCT+ isoforms of dystrobrevin are specialized components of the dystroglycan complex which render the complex sensitive to regulation by tyrosine kinases.
Balasubramanian
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Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Department of Neuroscience, Baltimore, MD 21205-2185, USA.
Fung
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Huganir
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RL
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002461:Cell Line, Transformed; D016189:Dystrophin / Q000737:chemistry / Q000276:immunology / Q000378:metabolism; D049029:Dystrophin-Associated Proteins; D007150:Immunohistochemistry; D008565:Membrane Proteins / Q000737:chemistry / Q000276:immunology; D009124:Muscle Proteins / Q000737:chemistry / Q000276:immunology; D018482:Muscle, Skeletal / Q000737:chemistry; D009479:Neuropeptides / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D011233:Precipitin Tests; D051381:Rats; D013347:Subcellular Fractions / Q000737:chemistry; D013570:Synaptic Membranes / Q000737:chemistry; D014018:Tissue Distribution; D014101:Torpedo / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism*
D016189:Dystrophin; D049029:Dystrophin-Associated Proteins; D008565:Membrane Proteins; D009124:Muscle Proteins; D009479:Neuropeptides; C098885:dystrobrevin; C091824:syntrophin; D014443:Tyrosine