Obscurin is a large cytoskeletal protein present in both epithelial and muscle cells. Its depletion, through knockdown or knockout, induces epithelial-to-mesenchymal transition (EMT)—a process associated with cancer development—alongside increased cell migration. Conversely, introducing select obscurin domains into epithelial cells reduces migration. Prior research has established that obscurin inhibits migration via two distinct pathways: activation of the RhoA/ROCK pathway and inactivation of the PI3K pathway. Here, we explore the interplay between these obscurin-linked pathways in MDCK cells, a previously unstudied epithelial cell type. We find that the addition of the obscurin C terminus leads to decreased migration, consistent with observations in other epithelial cells such as MCF-10A cells. Constructs lacking either the PH domain (linked to PI3K signaling) or the RhoGEF domain (linked to RhoA signaling) also reduce migration, suggesting functional redundancy. Surprisingly, simultaneous inhibition of both pathways still results in decreased cell velocity, indicating the presence of a third obscurin motif influencing motility. Further investigation reveals that obscurin crosslinks with intermediate filaments but not actin fibers, implicating cytoskeletal/membrane interactions in its regulatory function. Collectively, our findings suggest that obscurin modulates migration through at least three independent molecular mechanisms. Future work will aim to further characterize these pathways and their contributions to epithelial cell behavior.
Anbari et al. (Sun,) studied this question.