Mechanism of unidirectional movement of kinesin motors

Kinesin motors have been studied extensively both experimentally and theoretically. However, the microscopic mechanism of the processive movement of kinesin is still an open question. In this paper, we propose a hand-over-hand model for the processivity of kinesin, which is based on chemical, mechanical, and electrical couplings. In the model the processive movement does not need to rely on the two heads' coordination in their ATP hydrolysis and mechanical cycles. Rather, the ATP hydrolyses at the two heads are independent. The much higher ATPase rate at the trailing head than the leading head makes the motor walk processively in a natural way, with one ATP being hydrolyzed per step. The model is consistent with the structural study of kinesin and the measured pathway of the kinesin ATPase. Using the model the estimated driving force of ~ 5.8 pN is in agreements with the experimental results (5~7.5 pN). The prediction of the moving time in one step (~10 microseconds) is also consistent with the measured values of 0~50 microseconds. The previous observation of substeps within the 8-nm step is explained. The shapes of velocity-load (both positive and negative) curves show resemblance to previous experimental results.Comment: 22 pages, 6 figure

Model for processive movement of myosin V and myosin VI

Myosin V and myosin VI are two classes of two-headed molecular motors of the myosin superfamily that move processively along helical actin filaments in opposite directions. Here we present a hand-over-hand model for their processive movements. In the model, the moving direction of a dimeric molecular motor is automatically determined by the relative orientation between its two heads at free state and its head's binding orientation on track filament. This determines that myosin V moves toward the barbed end and myosin VI moves toward the pointed end of actin. During the moving period in one step, one head remains bound to actin for myosin V whereas two heads are detached for myosin VI: The moving manner is determined by the length of neck domain. This naturally explains the similar dynamic behaviors but opposite moving directions of myosin VI and mutant myosin V (the neck of which is truncated to only one-sixth of the native length). Because of different moving manners, myosin VI and mutant myosin V exhibit significantly broader step-size distribution than native myosin V. However, all three motors give the same mean step size of 36 nm (the pseudo-repeat of actin helix). Using the model we study the dynamics of myosin V quantitatively, with theoretical results in agreement with previous experimental ones.Comment: 18 pages, 7 figure

LHX1 as a potential biomarker regulates EMT induction and cellular behaviors in uterine corpus endometrial carcinoma

Objectives: To investigate the expression of LHX1 and its role as a biomarker in the diagnosis and prognosis of Uterine Corpus Endometrial Carcinoma (UCEC). Methods: The Cancer Genome Atlas (TCGA) database was used to detect the expression level of LHX1 in UCEC cells and tissues, and to find out the effect of LHX1 on prognosis. Co-expressed genes were then identified by Spearman correlation analysis, and the protein-protein interaction network was constructed using Cytoscape software. The R “clusterProfiler” package was used to conduct Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. A series of in vitro experiments were performed to evaluate LHX1 expression and detect UCEC cell proliferation, invasion, and migration. Western blotting was used to determine the effect of LHX1 on expression levels of Epithelial-Mesenchymal Transition (EMT)-related proteins. Results: LHX1 was upregulated in UCEC tissues and correlated with poor overall survival and disease-specific survival outcomes. Functional enrichment analysis suggested that genes co-expressed with LHX1 were enriched in cell adhesion. The expression of LHX1 was positively correlated with the expression levels of genes related to EMT induction and invasion. LHX1 can enhance the proliferation, migration, and invasion activities of UCEC cells in vitro, and alter the expression levels of EMT-related proteins. Conclusion: LHX1 expression was highly upregulated in UCEC cells and tissues, which was correlated with the prognosis of patients with UCEC. LHX1 may regulate UCEC progression at least in part by modulating EMT induction