Characterization of the tyrosine phosphorylation and distribution of dystrobrevin isoforms

Abstract

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 Cterminus, 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 3 and PYCT + splice variants, we generated antibodies against different regions of dystrobrevin. Here we show that the PYCT 3 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.z 1998 Federation of European Biochemical Societies.

Molecular Basis of Dystrobrevin Interaction with Kinesin Heavy Chain: Structural Determinants of their Binding

“…1 Dystrobrevins are characterized by a unique extreme carboxyl terminus and that of a-dystrobrevin can be phosphorylated. [8][9][10] Several distinct transcripts are derived from each gene by alternative splicing or initiation sites, generating a large family of dystrobrevin isoforms. a-Dystrobrevin is expressed predominantly in skeletal muscle, heart, lung and brain.…”

α-Dystrobrevin-1 recruits Grb2 and α-catulin to organize neurotransmitter receptors at the neuromuscular junction

“…ErbB is a tyrosine kinase; it might directly phosphorylate α-dystrobrevin-1 or stimulate phosphorylation indirectly by activating other kinases such as Src (Kuramochi et al, 2006;Ren et al, 2006;Vadlamudi et al, 2003). The latter possibility is supported by our finding that ectopic expression of a dominant-active Src mutant stimulates α-dystrobrevin-1 phosphorylation in HEK293 cells and the finding that Src phosphorylates purified α-dystrobrevin-1 in vitro (Balasubramanian et al, 1998). It is also possible that more than one kinase modifies α-dystrobrevin-1, and it would be beneficial to identify which kinase plays this role in various physiological and pathological processes in vivo.…”

“…Subsequent studies have identified α-dystrobrevin as a crucial mediator of the synaptic effects of the DGC and then successively focused on the α-dystrobrevin-1 isoform, the C-terminal extension of α-dystrobrevin-1 and phosphorylation of tyrosine residues in the C-terminal region (Balasubramanian et al, 1998;Blake et al, 1996;Grady et al, 2003Grady et al, , 2000Pawlikowski and Maimone, 2009;Schmidt et al, 2011). Here, we have extended this work in several ways.…”

“…α-Dystrobrevin-1 and α-dystrobrevin-2 are identical over most of their length, but α-dystrobrevin-1 bears a 176-amino-acid C-terminal extension comprising at least three tyrosine residues that are phosphorylated in vivo (Fig. 1A) (Balasubramanian et al, 1998;Blake et al, 1996). Evidence for a role of tyrosine phosphorylation in α-dystrobrevin function came from the demonstration that α-dystrobrevin-1 mutants lacking the three phosphorylatable tyrosine residues were deficient in their ability to stabilize AChRs in the postsynaptic membrane (Grady et al, 2003;Pawlikowski and Maimone, 2009).…”

Syntrophins and Dystrobrevins: Defining the Dystrophin Scaffold at Synapses

“…Such an elaborate alternative splicing scheme would not be expected of a protein that is only structural. Furthermore, the unique C-terminal tail of ·-dystrobrevin-1 is phosphorylated on tyrosine [53,65], suggesting that a kinase is involved in the function of this specific dystrobrevin isoform.…”