Analysis of Bmx tyrosine kinase signaling network in murine heart.

The Tec family of non‐receptor kinases is composed of 5 members (Tec, Bmx, Btk, Itk and Rlk) and was first identified in hematopoietic cells. Members of this family are known to participate in various aspects of B‐cell/T‐cell growth and differentiation. Despite this established role in the immune system, the actions of the Tec family in cardiac cells are virtually unexplored. We observed activation of one member, Bmx, in response to nitric oxide donor administration to the heart. To explore these findings, we used proteomics to characterize the proteins associated with Bmx to gain insights into its actions in the cardiac cell. Bmx‐associated proteins were isolated from mouse hearts using monoclonal antibody‐based immunoprecipitation (IP) and separated by 1D SDS PAGE (IgG alone IP was also performed; these proteins were excluded from the network). Following SYPRO staining, individual bands were excised over the vertical continuum of the gel, proteins trypsinized, and peptides analyzed by LC/MS/MS (QSTAR). Peptide spectra were acquired in data‐dependent mode and searched against the NCBI mouse database via Mascot. Our initial proteomic map of the Bmx signaling network hosts some previously recognized interactors, as well as novel potential signaling partners of Bmx. In particular we observed clusters of proteins involved in calcium handling, mitochondrial metabolism, nuclear regulation, and stress response. This study is the first examination of Tec family signaling in the heart and provides a preliminary description of the Bmx signaling network that can serve as a foundation for investigations into functions of this kinase in various cells types.