Poster Presentation 2014 International Biophysics Congress

Nano-scale spatial-temporal dynamics of paxillin and actin in 3D collagen matrices (#273)

Michelle Digman 1 , Enrico Gratton 1 , Chi-Li Chiu 1
  1. University of California Irvine, Irvine, CA, USA

Organization and dynamics of focal adhesion proteins have been well characterized in cells grown on two-dimensional (2D) cell culture surfaces which are debatably not a suitable representation of the anatomy and tissue microenvironment.  Limited imaging technologies capable of measuring protein interactions in real time and space for cells grown in 3D is a major impediment  in understanding how proteins function under different environmental cues. In this study, we applied the nano-scale precise imaging by rapid beam oscillation (nSPIRO) technique and combined the fluorescence correlation spectroscopy (FCS) and the Number and Brightness (N&B) methods to investigate paxillin and actin dynamics at focal adhesions in the 3D microenviroment.  Both MDA-MB-231 cells and U2OS cells produce elongated protrusions with high intensity regions of paxillin in cell grown in 3D collagen matrices. Using FCS we found higher percentage of slow diffusing proteins at these focal spots, suggesting assembling/disassembling processes.  In addition, the N&B analysis shows paxillin aggregated predominantly at these focal contacts which are next to collagen fibers. At those sites, actin showed slower apparent diffusion rate, which indicated that actin is either polymerizing or binding to the scaffolds in these locals. Our findings demonstrate that by multiplexing these techniques we have the ability to spatially and temporally quantify focal adhesion assembly and disassembly in 3D space and allow the understanding tumor cell invasion in a more complex relevant environment.