Alterations in plasma membrane ion channel structures stimulate NLRP3 inflammasome activation in APOL1 risk milieu

Abstract

We evaluated alterations in the structural configurations of channels and activation of nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 (NLRP3) inflammasome formation in apolipoprotein L1 (APOL1) risk and nonrisk milieus. APOL1G1-and APOL1G2-expressing podocytes (PD) displayed enhanced K + efflux, induction of pyroptosis, and escalated transcription of interleukin (IL)-1b and IL-18. APOL1G1-and APOL1G2-expressing PD promoted the transcription as well as translation of proteins involved in the formation of inflammasomes. Since glyburide (a specific inhibitor of K + efflux channels) inhibited the transcription of NLRP3, IL-1b, and IL-18, the role of K + efflux in the activation of inflammasomes in APOL1 risk milieu was implicated. To evaluate the role of structural alterations in K + channels in plasma membranes, bioinformatics studies, including molecular dynamic simulation, were carried out. Superimposition of bioinformatics reconstructions of APOL1G0, G1, and G2 showed several aligned regions. The analysis of pore-lining residues revealed that Ser342 and Tyr389 are involved in APOL1G0 pore formation and the altered conformations resulting from the Ser342Gly and Ile384Met mutation in the case of APOLG1 and deletion of the Tyr389 residue in the case of APOL1G2 are expected to alter pore characteristics, including K + ion selectivity. Analysis of multiple membrane (lipid bilayer) models of interaction with the peripheral protein, integral membrane protein, and multimer protein revealed that for an APOL1 multimer model, APOL1G0 is not energetically favorable while the APOL1G1 and APOL1G2 moieties favor the insertion of multiple ion channels into the lipid bilayer. We conclude that altered pore configurations carry the potential to facilitate K + ion transport in APOL1 risk milieu.Abbreviations AA, amino acid; APOL1, apolipoprotein L1; APOL1G0, APOL1 nonrisk allele; APOL1G1 and G2, APOL1 risk alleles/

Vascular Inflammation in Lungs of Patients with Fatal Coronavirus Disease 2019 (COVID-19) Infection: Possible role for the NLRP3 inflammasome

“…As NLRP3 inflammasome driven pyroptosis is being considered to play a leading role in the pathogenesis of multi-organ failure with COVID-19 (22), there is some speculation on the mechanisms by which inflammasome activation occurs upon SARS-CoV-2 infection. One possibility is that the SARS-CoV-2 spike protein’s binding to cell surface-expressed angiotensin-converting enzyme 2 (ACE2) directly triggers its enzymatic activation and alters membrane polarity that can result in activation of NLPR3 inflammasome (18). Or NLRP3 could be activated via Angiotensin II which is reported to facilitate the assembly of the inflammasome.…”

The Relationship between APOL1 Structure and Function: Clinical Implications

“…14 Recently, Jha et al modeled the full-length structure of APOL1 proteins using ab inito methods followed by MD simulations. 55 In addition to confirming the Cterminal helical conformation adopted by APOL1s, the model showed the role of variant residues (S342 and I384 in G1) and (Y389 in G2) in establishing the channel function of APOL1. Overall, the protein conformational changes induced by the G1 and G2 variants could disrupt protein-protein interaction that is necessary for the cellular homeostatic function of APOL1 predisposing to CKD pathogenesis.…”

“…APOL1 is a membrane-associated protein with several putative transmembrane domains 21,[56][57][58] and localizes to multiple cellular membrane environments, including endo-lysosomes, golgi-ER, mitochondria and plasma membranes. 14,20,23,31,32,[34][35][36]55,[58][59][60][61] In this membrane environment, full length APOL1 proteins, especially the G1 and G2 formed large molecular weight oligomers as judged by native non-reducing PAGE. Such oligomers may mediate cellular cascade leading to cytotoxicity.…”

Towards the NMR solution Structure and the Dynamics of the C-terminal Region of APOL1 and its G1, G2 Variants with a Membrane Mimetic

“…This conformation can expose the C-terminal region of APOL1 to the cytoplasm, where interaction with SNAREs and other effector proteins is feasible. Existing data suggest that APOL1 interacts with multiple cellular organelle membranes including ER-Golgi network (20,55), mitochondria (14,16,21,56), endo-lysosomal system (6,18,19,50,52) and plasma membranes (13,17,30). Membrane composition and hence protein structure and orientation can differ among these different subcellular environments (57,58).…”

“…The protein structures of the reference APOL1 (G0) and of the G1 and G2 variants have not been experimentally studied. Previously, our group and others have used computational methods using template-based and ab initio modeling to characterize the structure of APOL1 protein domains (6,26–30). The domain organization of APOL1 is as follows ( Fig.…”