α-Dystrobrevin distribution and association with other proteins in human promyelocytic NB4 cells treated for granulocytic differentiation.

Dystrobrevins (DBs) bind directly to dystrophin and are prominent components of the dystrophin-associated protein complex (DAPC) that links the cytoskeleton to the extracellular matrix. They are involved in brain development, synapse formation and plasticity, as well as water and ion homeostasis. However, the role of DB in non-muscular cells is not clear. In this study, we show that different α-dystrobrevin isoforms are present in promyelocytic leukemia (NB4) cells. Only the biggest α-dystrobrevin isoform (DB-α), which can be important for its function, was expressed in the membrane fraction of NB4 cells; the other α-DB isoforms were found in the hydrophilic cell fractions. Employing the immunoprecipitation and mass spectrometry, we identified novel α-DB-interacting proteins involved in cytoskeleton reorganization (actin, tropomyosin, gelsolin, tubulin) and signal transduction process (stathmin, prohibitin, RIBA) during proliferation and differentiation of NB4 cells. Our results suggest that α-DB isoforms play a central role in cytoskeleton reorganization via their multiple interactions with actin and actin-associating proteins and may participate in signal transduction process during NB4 cell granulocytic differentiation via directly and non directly associated proteins.