ABSTRACT
BACKGROUND: To date, ANLN has definite roles in altering cell shape, regulating cell-cell junction integrity in interphase and stabilizing actomyosin contractile rings in cytokinesis, but its effects on cell mechanical properties and on cytoskeletal proteins have rarely been reported. OBJECTIVE: To investigate the effect of ANLN deletion on the mechanical properties and cytoskeleton of interphase Hela cells. METHODS: Surface elastic modulus and membrane rupture force of normal untreated Hela cells and ANLN RNA stably knocked down Hela cells were measured by atomic force microscopy. We screened for the cells that stably expressed mCherry-Myosin II A, and observed the distribution characteristics of cytoskeletal proteins by laser scanning confocal microscopy. RESULTS AND CONCLUSION: (1) The elastic modulus of Hela cells with ANLN stably knocked down was significantly higher than that of normal Hela cells, and the elastic modulus of normal cells were more prone to polar distribution (gradually decreasing between the two poles) than that of ANLN knockdown Hela cells. However, there was no significant difference in the membrane rupture force at the long-axis edge region between the two groups. (2) Myosin IIA lowly expressed in the marginal region of ANLN knockdown cells. (3) The actin fibers tended to be scattered in the near-bottom cell-cell junction region of the ANLN knockdown group, and there were no obvious intracellular fibers bundles arranging along the long axis. The cell gap tended to enlarge in the middle layer. To conclude, ANLN knockdown cells have the greatest impact in the marginal region, the deficiency of ANLN leads to a more frequent remodeling in the cell marginal region, and the cells need to accumulate more cytoskeletal proteins and binding proteins to stabilize the cell state, resulting in higher modulus of elastics.
ABSTRACT
The dynamic performance of a skeletal muscle depends on the length-force and force-velocity relationships. The length-force relationship of muscle was described by Blix for the first time. The contractile elements of muscles produce the active length-force curve. The objective of this study is to determine the length-force relationship of the rabbit's soleus muscle and changes of tetanic force according to the position of ankle joint. The amount of excursion of the soleus muscle for full range of motion of the ankle joint was 25 mm. The ratio of excursion compared to the length of neutral position was 24%. That means that the soleus muscle has large amount of excursion that is responsible for producing active force throughout the whole range of ankle motion. The length at which active force of the muscle is maximal is called optimum length(Lo). The ratio of the optimum length compared to the length of neutral position was 98%. This means that the active force of the soleus muscle was maximal at the position of slight plantarflexion(about 2 degrees of plantarflexion). The value of the tetanic force was 3.1kg/cm2 in average, and the active length-force curve showed asymmetrical shape. The effective range is a length change from minimal point of zero active force to maximal point of zero active force. In this study, the minimal point of zero active force was 11mm shorter and maximal point of zero active force was 13mm longer than optimum length. Therefore, the effective range was 24mm. Active force increased abruptly at which muscle length was 90% of neutral length. At that point, active force was less than 20% of maximal tetanic force.