The bicellular tensile force sorts the localization of LSRs in bicellular and tricellular junctions

Lipolysis-stimulated lipoprotein receptors (LSRs) localize to tricellular tight junctions. Recent studies have shown that changes in the localization and expression profiles of LSRs are associated with malignancy of endometrial carcinomas, although the precise mechanisms by which malignant progression induces changes in the localization of LSRs are still unknown. In this study, we found that changes in cell tension correlated with alterations in the junctional localization of LSRs in endometrial cancer Sawano cells. At high cell densities, myosin phosphatase target subunit 1 (MYPT1) localized to bicellular junctions, whereas activated myosin regulatory light chain 2 (MRLC2) was dislocated from these regions, suggesting that circumferential tensile forces decreased at high cell densities. Under these conditions, LSRs localized to tricellular junctions. In contrast, a phosphorylated form of MRLC2 localized to bicellular regions, while MYPT1 was excluded from these regions, suggesting that tensile forces formed along the circumferential edge at low cell densities. It is noteworthy that, when cells were cultured under these conditions, LSRs localized to bicellular regions. Upon treatment with a myosin inhibitor, LSR localization in bicellular junctions decreased at low cell densities. Overall, our results indicate that the modulation of cellular tension was involved in the translocation of LSRs from bicellular to tricellular tight junctions.