Expression of DOCK10.1 protein revealed with a specific antiserum: insights into regulation of first exon isoforms of DOCK10.

DOCK10, a guanine-nucleotide exchange factor (GEF) for Rho GTPases, represents the example of a gene that gives rise to alternative first exon mRNA isoforms, named DOCK10.1 and DOCK10.2. Expression of human DOCK10.2 protein in cell lines, and its induction by interleukin-4 (IL-4) in normal B lymphocytes and chronic lymphocytic leukemia (CLL) cells, were previously demonstrated using an antiserum raised against a peptide encoded by sequences from exon 1.2. Here, expression of human DOCK10.1 protein was demonstrated using an antiserum raised against a peptide encoded by sequences from exon 1.1. Specificity of the DOCK10.1 and DOCK10.2 antisera for their respective isoforms was demonstrated using transfected human 293 T cells. Their specificity for endogenous DOCK10 was strongly suggested by the high significance of the correlations between the levels of their expected signals at the molecular size of 250 kDa and the levels of DOCK10.1 and DOCK10.2 mRNAs, respectively, in human hematopoietic cell lines. Specificity of the DOCK10.1 antiserum for DOCK10 was also demostrated in mouse using the DOCK10 knockout model. The DOCK10.1 protein was induced by IL-4 in CLL cells, which demonstrates that the mechanism by which IL-4 regulates DOCK10 is not isoform-specific. Last, to get insights into differential regulation of the DOCK10 isoforms, their protein levels in cell lines were compared with their gene expression profiles retrieved from the Cancer Cell Line Encyclopedia (CCLE), leading to the identification of BCL3 and KLF12 as potential transcriptional regulators of DOCK10.1 and DOCK10.2, respectively.