Identification and characterisation of subtype-specific anti-N-CoR OSGEP protease in acute myeloid leukaemia (AML-M5) cell lineage.

Acute myeloid leukemia (AML) is a neoplastic disorder of the myeloid stem cell and is most commonly diagnosed in children and young adults. N-CoR is an essential protein that regulates transcriptional repression in normal myeloid cell development Mutations or loss of function in the N-CoR gene result in the abnormal expression of critical genes involved in cell proliferation, contributing to leukemogenic transformation and the development of malignancy in acute myeloid leukemia subtype M5 (AML-M5). This study was aimed to elucidate the mechanism of N-CoR degradation by O-sialo-glycoprotein endopeptidase (OSGEP), a protease that is active in AML-M5 cells only. The AML-M5-specific proteases were isolated using HPLC size exclusion chromatography and anti-N-CoR OSGEP antibodies. In vitro experiments were performed to test the degradation of recombinant N-CoR protein by OSGEP protease. The protease's identity and composition were analyzed via mass spectrometry. Study involved transfection studies using various cell lines to evaluate the subtype-specific activity of OSGEP based on N-CoR expression levels. Study findings revealed OSGEP protease to cleave N-CoR in AML-M5 cells. Mass spectrometry confirmed the identity and composition of a purified, functionally active form of the OSGEP protease. The transfection studies proved that N-CoR was the only protein of the two that OSGEP protease acted on selectively in AML-M5 cells thus proving its specificity in the subtype of cells. Findings of present study suggests that OSGEP protease-mediated N-CoR degradation is an important factor in the development of AML-M5. Current study highlights N-CoR degradation by OSGEP as a key molecular event in AML-M5 and proposes the N-CoR protease as a potential diagnostic and therapeutic biomarker for this leukemia subtype.