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.
Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Department of Neuroscience, Baltimore, MD 21205-2185, USA.
S
S
Balasubramanian
E T
ET
Fung
R L
RL
Huganir
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