The ASC Speck and NLRP3 Inflammasome Function Are Spatially and Temporally Distinct

Abstract

Although considered the ternary inflammasome structure, whether the singular, perinuclear NLRP3:ASC speck is synonymous with the NLRP3 inflammasome is unclear. Herein we report that the NLRP3:ASC speck is not required for nigericin-induced inflammasome activation, but facilitates and maximizes IL-1β processing. Further, the NLRP3 agonists H2O2 and MSU elicited IL-1β maturation without inducing specks. Notably, caspase-1 activity is spatially distinct from the speck, occurring at multiple cytoplasmic sites. Additionally, caspase-1 activity negatively regulates speck frequency and speck size while speck numbers and IL-1β processing are negatively correlated, cyclical, and can be uncoupled by NLRP3 mutations or inhibiting microtubule polymerization. Finally, when specks are present, caspase-1 is likely activated after leaving the speck structure. Thus, the speck is not the NLRP3 inflammasome itself, but is instead a dynamic structure which may amplify the NLRP3 response to weak stimuli by facilitating the formation and release of small NLRP3:ASC complexes which in turn activate caspase-1.

lncRNA HOTAIR promotes ROS generation and NLRP3 inflammasome activation by inhibiting Nrf2 in diabetic retinopathy

“…Proteins from cells or supernatants were prepared as previously described [26,27] or using a nuclear and cytoplasmic protein extraction kit (P0028; Beyotime Biotechnology) according to the manufacturer's instructions. The detection of protein form supernatants is same in all groups to ensure the loading protein level is coincident.…”