The expression and functional characterization associated with cell apoptosis and proteomic analysis of the novel gene MLAA-34 in U937 cells

MLAA-34 is a novel acute monocytic leukemia (M5)-associated antigen (MLAA)that plays a role in the apoptosis of U937 cells. However, the expression andmolecular mechanism of MLAA-34 in U937 cells remain largely unclear. Here, weutilized three strategies to gain insight into the expression and molecular functionsof MLAA-34 and to identify its interacting proteins and pathways involved in thefine-tuning of the MLAA-34 response. Western blot analysis was performed to assessthe expression of MLAA-34 in 41 cell lines and five mixed cell types, which revealedthat MLAA-34 is most strongly expressed in U937 cells. Immunostaining indicatedthat MLAA-34 is localized in the cytoplasm and cell membrane. Furthermore, lentivirus-mediatedoverexpression of MLAA-34 in the U937 cell line led to significant suppressionof apoptosis and increased the potential of tumorigenicity. Co-immunoprecipitation(Co-IP), shotgun and bioinformatic analysis identified 256 proteins and 225 ofthem were annotated by gene ontology categories. This analysis revealed 71 proteinsinvolved in cell apoptosis or proliferation of biological processes and signalingpathways. Moreover, the effect of MLAA-34 apoptosis may be through interactionwith the Ras, Wnt, calcium and chemokine signaling pathways and thirteen of theannotated proteins may interact with MLAA-34 and participate in carcinogenesisdirectly. This study provides a basis for a better understanding of the molecularmechanism and proteomics in the inhibition of apoptosis by MLAA-34 in U937 cellsand indicates that MLAA-34 may be a potential candidate for the early diagnosisand therapeutic application of M5.