The discoidin domain receptors, DDR1 and DDR2, are key signaling receptors for the
extracellular matrix protein collagen. The interactions of cells with collagen are difficult to study because
of the difficulty to obtain native collagen fibers for in vitro studies. Thus, in vitro studies often use acidsoluble collagens in the form of single triple helices, which are not representative of the densely packed
insoluble collagen fibers found in tissues. In this protocol, we describe a method that allows stimulating
DDR1 locally with collagen-coated beads. Latex beads are first coated with acid-soluble collagen, then
added to cells expressing DDR1. Recruitment of DDR1 to the beads and collagen-induced DDR1
phosphorylation is visualized by immunofluorescence microscopy on a widefield microscope. In this
method, densely packed collagen is presented to cells in an insoluble form. Bead coating is easy to
perform, and this method thus presents a straightforward protocol with which to study local recruitment
of collagen receptors to insoluble collagen.