Defining the role of the RGS12 locus in macrophage function

ABSTRACT: Macrophages are vital components of a diverse and extensive set of physiological processes, and rely on precise response to both internal and external cues to perform their functions. G-protein signaling comprises a significant proportion of these functional cues, and thus is a significant and consequential mechanism of macrophage regulation. Regulators of G-protein signaling (RGS) proteins are a family of related proteins that exert control over G-protein pathways by accelerating the termination of signaling cascades. RGS12 is the largest member of the RGS family and possesses a number of protein-protein interaction domains in addition to this G-protein regulation capability. The goal of this proposal is to investigate how RGS12 influences macrophage function in the context of a leukocyte-rich structure known as a granuloma. In response to persistent inflammatory stimuli including mycobacterial infection, macrophages aggregate into a granuloma structure, and a subset of these cells undergo a transformation into epithelioid macrophages, which are critical to the integrity of the granuloma structure. Using the zebrafish-Mycobacterium marinum model and available human tuberculosis (TB) patient cohort datasets, we have found that the zebrafish ortholog rgs12b is enriched in the epithelioid macrophage population and that RGS12 is associated with increased TB severity, while preliminary data suggests that loss of rgs12b disrupts macrophage epithelioid transformation and granuloma bacterial containment. Thus, we hypothesize that rgs12b is an important regulator of macrophage function and identity, and will utilize the zebrafish-M. marinum model to investigate the mechanism of this interaction in the context of a mycobacterial granuloma. Completion of the proposed work will represent a significant contribution to our understanding of how macrophage behavior and G-protein signal regulation can alter function. The findings will be relevant to the development of host-direct therapies targeting the granuloma structure, and could also extend to a number of blood and lung-related disorders in which RGS protein irregularities have been implicated.