Wiskott Aldrich syndrome protein regulates non-selective autophagy and mitochondrial homeostasis in human myeloid cells

Abstract

The actin cytoskeletal regulator Wiskott Aldrich syndrome protein (WASp) has been implicated in maintenance of the autophagy-inflammasome axis in innate murine immune cells. Here, we show that WASp deficiency is associated with impaired rapamycin-induced autophagosome formation and trafficking to lysosomes in primary human monocyte-derived macrophages (MDMs). WASp reconstitution in vitro and in WAS patients following clinical gene therapy restores autophagic flux and is dependent on the actin-related protein complex ARP2/3. Induction of mitochondrial damage with CCCP, as a model of selective autophagy, also reveals a novel ARP2/3-dependent role for WASp in formation of sequestrating actin cages and maintenance of mitochondrial network integrity. Furthermore, mitochondrial respiration is suppressed in WAS patient MDMs and unable to achieve normal maximal activity when stressed, indicating profound intrinsic metabolic dysfunction. Taken together, we provide evidence of new and important roles of human WASp in autophagic processes and immunometabolic regulation, which may mechanistically contribute to the complex WAS immunophenotype.

Self-DNA Sensing by cGAS-STING and TLR9 in Autoimmunity: Is the Cytoskeleton in Control?

“…Some evidence suggests that actin may also be important in the late stage of phagosomal closure, as shown by the requirement for Arp2/3 during selective autophagy ( 79 ). More recently, Wiskott-Aldrich syndrome protein (WASp) has been linked to the global orchestration of both general and selective autophagy in myeloid cells ( 80 , 81 ). Even if a detailed mechanism of WASp-autophagy connections remains to be explored, it can be extrapolated that deregulation of actin dynamics (see below) will impact cGAS-STING signaling in phagocytes.…”

“…Compatibly with its abundance and the poor expression of the other NPFs, WASp was shown to multitask at the cell periphery and intracellularly in immune cells ( 80 , 118 ). WASp regulates multiple immune cell functions, ranging from BCR and TCR receptor signaling in lymphocytes to migration and phagocytosis in myeloid cells ( 81 ). Defects in these processes provide a logical explanation for weak responses to pathogens and increased susceptibility to infections.…”

“…Moreover, by interacting with phosphoinositides ( 128 ), WASp may participate in cGAS anchoring at the plasma membrane, a mechanism that prevents recognition of cytosolic self-DNA in myeloid cells ( 129 ). Recently it was observed that the formation of actin cages around damaged mitochondria and mitophagy are reduced in WASp null cells ( 81 ), suggesting there may be an exaggerated release of mtDNA in the cytosol of WASp deficient cells that could contribute to overall chronic activation of IFN genes. Finally, WASp is also present inside the nucleus.…”

Molecular Tuning of Actin Dynamics in Leukocyte Migration as Revealed by Immune-Related Actinopathies

“…In this context, the WASP-ARP2/3 pathway appears crucial in the assembly of podosomes, while the WAVE complex is dispensable. Indeed both WASP and ARPC1B deficiencies are associated with the defective assembly of podosomes by monocyte-derived macrophages ( 19 , 84 ). In contrast, macrophages from Nckap1l -KO mice have a preserved ability to assemble podosomes although they display multiple defects in lamellipodia, focal adhesions and endocytosis ( 47 ).…”

“…Reconstitution experiments in WAS patient-derived macrophages using micro-injections of full-length human WASP sequence suggested that the chemotactic response to the cytokine colony stimulating factor-1 is dependent on WASP-driven assembly of podosomes ( 159 ). To date, studies of WASP revealed its key role in podosome assembly in multiple cellular systems beyond macrophages: immature DCs ( 80 ), THP-1 ( 19 ) and T cells ( 89 ). Moreover, experiments using RNA interference to induce partial down-regulation of the intracellular WASP level in DCs led to compromised podosome formation ( 160 ), indicating that a precise regulation of WASP expression might be crucial for assembly of podosomes.…”