Product Uses Include
The most reproducible and accurate method of determining the amount of filamentous actin (F-actin) content versus free globular-actin (G-actin) content in a cell population is to use Western blot quantitation of F-actin and G-actin cellular fractions (1-4). The general approach is to homogenize cells in F-actin stabilization buffer, followed by centrifugation to separate the F-actin from G-actin pool. The fractions are then separated by SDS-PAGE and actin is quantitated by Western blot. The final result gives the most accurate method of determining the ratio of F-actin incorporated into the cytoskeleton versus the G-actin found in the cytosol. This kit contains all the reagents needed to perform this assay.
The kit contains sufficient materials for 30-100 assays depending assay setup and includes reagents for positive and negative controls. The following components are included:
Swiss 3T3 cells were grown to 50% confluency in DMEM / 10% FBS at 37°C/5% CO2. Cells were untreated (lanes 1P and 1S) or treated with 0.1 µM of the actin polymerizing drug jasplakinolide for 30 minutes at 37°C/5% CO2 (lanes 2P and 2S). Cells were lysed and processed into supernatant (S) and pellet (P) fractions and ana-lysed by western blot quantitation of actin protein according to the G-actin/F-actin In Vivo Assay Kit instructions.
Panel 1: In untreated Swiss 3T3 cells, 45% of actin is soluble G-actin (1S) and 55% is insoluble F-actin (1P). This agrees with published data (3).Panel 2: In Swiss 3T3 cells treated with the actin polymerizing drug jasplakinolide, only 5% of actin remains in the soluble G-actin fraction (2S) while 95% is found in the insoluble F-actin pellet fraction (2P). Lanes 50, 20 and 10 represents 50ng, 20ng and 10 ng of G-actin standard. M represents molecular weight markers (molecular weights are shown to the right of the blot).
Asahara et al., 2013. Ras-related C3 botulinum toxin substrate 1 (RAC1) regulates glucose-stimulated insulin secretion via modulation of F-actin. Diabetologia. doi: 10.1007/s00125-013-2849-5.
Ni et al., 2013. The role of RhoA and cytoskeleton in myofibroblast transformation in hyperoxic lung fibrosis. Free Radical Biology and Medicine. doi: http://dx.doi.org/10.1016/j.freeradbiomed.2013.03.012.
Ramachandran et al., 2013. JunB mediates basal- and TGFb1-induced smooth muscle cell contractility. PLoS ONE. 8(1): e53430.
Shuang et al., 2013. Destrin deletion enhances the bone loss in hindlimb suspended mice. E. J. Appl. Physiol. 113, 403-410.
Malenda et al., 2012. Statins Impair Glucose Uptake in Tumor Cells. Neoplasia. 14, 311–323.
Fan et al., 2012. A role for γS-crystallin in the organization of actin and fiber cell maturation in the mouse lens. FEBS. J. 279, 2892-2904.
Liu et al., 2012. TLR2 Is a Primary Receptor for Alzheimer's Amyloid β Peptide To Trigger Neuroinflammatory Activation. J. Immunol. 188, 1098-1107.
Chand et al., 2012. C-terminal region of teneurin-1 co-localizes with dystroglycan and modulates cytoskeletal organization through an extracellular signal-regulated kinase-dependent stathmin- and filamin A-mediated mechanism in hippocampal cells. Neuroscience. 219, 255-270.
Rapier et al., 2010. The extracellular matrix microtopography drives critical changes in cellular motility and Rho A activity in colon cancer cells. Cancer Cell Int. 10, 24.
Meeks et al., 2005. Heat shock protein 20-mediated force suppression in forskolin-relaxed swine carotid artery. Am. J. Physiol. 288, C633-C639.
Zhang et al., 2005. Activation of the Arp2/3 complex by N-WASP is required for actin polymerization and contraction in smooth muscle. Am. J. Physiol. 288, C1145-C1160.
Chen et al., 2004. Protective effect of phosphatidylinositol 4,5-bisphosphate against cortical filamentous actin loss and insulin resistance induced by sustained exposure of 3T3-L1 adipocytes to insulin. J. Biol. Chem. 279, 39705-39709.
Tang and Gunst, 2004. The small GTPase Cdc42 regulates actin polymerization and tension development during contractile stimulation of smooth muscle. J. Biol. Chem. 279, 51722-51728.
Searles et al., 2004. Actin cytoskeleton organization and poststranscriptional regulation of endothelial nitric oxide synthase during cell growth. Circ. Res. 95, 488-495.
Tu et al., 2003. Migfilin and Mig-2 link focal adhesions to filamin and the actin cytoskeleton and function in cell shape modulation. Cell. 113, 37-47.
Question 1: At which step can the assay be stopped?
Answer 1: The assay cannot be stopped until after the 100,000 x g spin for 1 hour at 37°C. After this high speed centrifugation, the supernatant (G-actin) can be mixed with SDS loading buffer and frozen for later use. The pellet (F-actin) should be resuspended with a depolymerizing agent and water and then mixed with SDS loading buffer and frozen for later use. Upon freezing, F-actin depolymerizes, so it is necessary to separate the F-actin from the G-actin before freezing samples to isolate samples for an accurate measurement of F-actin and G-actin ratios.
Question 2: How sensitive is this assay?
Answer 2: The assay can detect as small as a 15% shift in G-actin to F-actin ratio. Each condition should be performed in duplicate and repeated several times as assay reproducibility can vary by 10-20% between experiments.
If you have any questions concerning this product, please contact our Technical Service department at email@example.com