Investigation of the effect of CLpP inhibition on integrin signaling in multiple myeloma cells

Multiple myeloma (MM) is a hematological malignancy characterized by the excessive proliferation of plasma cells producing monoclonal antibodies in the bone marrow. As current treatments do not have curative potential and most patients experience relapse, MM is considered an incurable malignancy. Therefore, a good understanding of the molecular mechanisms underlying MM biology is essential. MM cells require the maintenance of mitochondrial functions to proliferate and produce monoclonal antibodies. However, exposure to mitochondrial stressors, such as hypoxia, reactive oxygen species (ROS) and increased protein homeostasis, can lead to mitochondrial dysfunction. The mitochondrial unfolded protein response (UPRmt), which plays a role in maintaining mitochondrial homeostasis, involves the kazeinolitik protease proteolytic subunit (CLpP) mitoprotease, which eliminates oxidized proteins and degrades misfolded or unfolded polypeptides to ensure quality control surveillance of the mitochondria. Additionally, the role of VLA-4 (α4 β1), VLA-5 (α5β1) and integrin β7 integrins has been shown in regulating MM cell adhesion, migration, homing, invasion and chemoresistance. However, the effect of CLpP on VLA-4 and VLA-5 integrins in MM cells is unknown. Therefore, the aim of this study was to investigate the relationship between CLpP and VLA-4 and VLA-5 integrins. In our study, the inhibition of CLpP was achieved using shRNA lentiviral vectors in human MM cell lines NCI H929 and RPMI 8226. The effect of this inhibition on mRNA expression levels of VLA-4, VLA-5 and integrin β7 from the integrin family was determined by quantitative simultaneous PCR (qPCR). The results revealed that the inhibition of CLpP in MM cells led to a significant decrease in mRNA expression levels of VLA-4 and VLA-5 compared to control cells. Therefore, it is concluded that CLpP stimulates the expression of VLA-4, VLA-5 and integrin β7 integrins in MM cells.