RHOA-mediated mechanical force generation through Dectin-1

Dectin-1 (Dendritic Cell associated C-type Lectin 1) is an innate immune pattern recognition receptor which recognizes β-glucan on the Candida albicans (C. albicans) cell wall. Recognition of β-glucan by immune cells leads to phagocytosis, oxidative burst, cytokine and chemokine production. We looked for specific mechanisms that coordinate phagocytosis downstream of Dectin-1 leading to actin reorganization and internalization of fungus. We found that stimulation of Dectin-1 by soluble β-glucan leads to mechanical force generation and areal contraction in Dectin-1 transfected HEK-293 cells and M1 macrophages. With inhibitor studies, we found this force generation is a SYK (Spleen Tyrosine Kinase)-independent, SFK (SRC Family Kinase)-dependent process mediated through the RHOA (Ras homolog family member type A)-ROCK (Rho associated coiled-coil containing protein kinase)-MLC (Myosin light chain) pathway. We confirmed activation of RHOA downstream of Dectin-1 using activity assays and stress fiber formation. Through phagocytosis assays, we found direct evidence for the importance of RHOA-ROCK-MLC signaling in the process of phagocytosis of C. albicans.