Key Points• DDR2 regulates the directional migration of neutrophils in 3D collagen matrices, but not on 2D surfaces. • DDR2 regulates directionality through increased metalloproteinase secretion and generation of collagen-derived chemotactic peptide gradients.Neutrophils express a variety of collagen receptors at their surface, yet their functional significance remains unclear. Although integrins are essential for neutrophil adhesion and migration on 2-dimensional (2D) surfaces, neutrophils can compensate for the absence of integrins in 3-dimensional (3D) lattices. In contrast, we demonstrate that the inhibition of the tyrosine-kinase collagen receptor discoidin domain receptor 2 (DDR2) has no impact on human primary neutrophil migration on 2D surfaces but is an important regulator of neutrophil chemotaxis in 3D collagen matrices. In this context, we show that DDR2 activation specifically regulates the directional migration of neutrophils in chemoattractant gradients. We further demonstrate that DDR2 regulates directionality through its ability to increase secretion of metalloproteinases and local generation of collagen-derived chemotactic peptide gradients. Our findings highlight the importance of collagen-derived extracellular signaling during neutrophil chemotaxis in 3D matrices. (Blood. 2013;121(9):1644-1650)
IntroductionNeutrophils exhibit the ability to maintain robust migration under a wide array of distinct environmental conditions. For example, by increasing the rate of actin polymerization, neutrophils lacking integrins are able to retain normal migration speeds in 3D environments. 1,2 We set out to determine the role of another collagen receptor family, the discoidin domain receptors (DDRs), during neutrophil chemotaxis. The DDR family is composed of 2 members, DDR1 and DDR2. DDRs are homodimeric receptor tyrosine kinases that bind to triple-helical collagen fibers through a domain similar to discoidin 1 of the social amoeba Dictyostelium discoideum. 3,4 On binding to collagen, DDRs become activated and serve as docking sites for many signaling pathways. 5 A common outcome after DDR activation is the increase in metalloproteinase (MMP) secretion and collagen rearrangement. [6][7][8][9] As a consequence, DDR1 and DDR2 have both been associated with metastasis during tumor progression. 6 Similarly, DDR1 overexpression has been shown to enhance lymphocyte migration. 10,11 However, the mechanism underlying the enhanced leukocyte migration remains unknown.We show that circulating human primary neutrophils solely express DDR2 and establish that DDR2 regulates the ability of neutrophils to migrate directionally toward chemoattractants in a collagen I matrix. DDR2 activation induces increased MMP secretion, leading to the generation of collagen-derived chemotactic peptides that are poised to form local gradients and enhance neutrophil persistence.
Methods
Isolation of human blood neutrophilsBlood was collected from anonymous healthy donors enrolled in the National Institutes of Health Blood Bank research prog...