Mitofusin 2 regulates neutrophil adhesive migration and the actin cytoskeleton

Abstract

Neutrophils rely on glycolysis for energy production. How mitochondria regulate neutrophil function is not fully understood. Here, we report that mitochondrial outer membrane protein Mitofusin 2 (Mfn2) regulates neutrophil homeostasis and chemotaxis in vivo. Mfn2-deficient neutrophils are released from the hematopoietic tissue, trapped in the vasculature in zebrafish embryos, and not capable of chemotaxis. Consistently, human neutrophil-like cells deficient with MFN2 fail to arrest on activated endothelium under sheer stress or perform chemotaxis on 2D surfaces. Deletion of Mfn2 results in a significant reduction of neutrophil infiltration to the inflamed peritoneal cavity in mice. Mechanistically, MFN2-deficient neutrophil-like cells display disrupted mitochondria-ER interaction, heightened intracellular calcium levels, and elevated Rac activation after chemokine stimulation. Restoring mitochondria-ER tether rescues the abnormal calcium levels, Rac hyperactivation, and chemotaxis defect resulted from MFN2 depletion. Finally, inhibition of Rac activation restores chemotaxis in MFN2-deficient neutrophils. Altogether, we identified that MFN2 regulates neutrophil migration via maintaining mitochondria-ER interaction to suppress Rac activation and uncovered a previously unrecognized role of MFN2 in regulating cell migration and the actin cytoskeleton.

A cancer ubiquitome landscape identifies metabolic reprogramming as target of Parkin tumor suppression

“…Specifically, cortical mitochondria act as regional energy sources ( 36 , 37 ) fueling membrane lamellipodia dynamics, FA turnover, and Rho guanosine triphosphatase (GTPase) signaling ( 38 ) to increase cell movements ( 39 ). Consistent with a role of Parkin in mitochondrial dynamics via ubiquitination of MFN proteins ( 40 ), MFN2 and RHOT1 have been recognized as important effectors of tumor chemotaxis ( 41 ), influencing Myc-driven metastasis ( 42 ).…”

Integrin Regulators in Neutrophils

“…This was further demonstrated by neutrophil recruitment defects in MFN2 knockout zebrafish and MFN2 flox/flox MRP8-cre mice [223]. MFN2 knockdown dHL60 cells showed a defect in adhesion on inflamed human umbilical vein endothelial cells (HUVEC) [223]. Using microfluidic devices, our group has shown that MFN2 knockdown dHL60 cells have defects in slow rolling and arrest on P-selectin/ICAM-1 and P-selectin/ICAM-1/IL8 substrates, respectively, suggesting a role of MFN2 in regulating β2 integrin activation on neutrophils [224].…”

“…It was found that interfering with MFN2 expression using shRNA can significantly suppress the chemotaxis of neutrophil-like DMSOdifferentiated HL-60 (dHL60) cells [222]. This was further demonstrated by neutrophil recruitment defects in MFN2 knockout zebrafish and MFN2 flox/flox MRP8-cre mice [223]. MFN2 knockdown dHL60 cells showed a defect in adhesion on inflamed human umbilical vein endothelial cells (HUVEC) [223].…”

A robust and flexible CRISPR/Cas9-based system for neutrophil-specific gene inactivation in zebrafish

“…We could not observe mitochondrial morphology or related molecular/metabolic changes in any neutrophils with gene knockouts, and our work in zebrafish stopped with phenotypic observation. We only used zebrafish data for initial discovery, and the rest of the work was completed in human cells (Zhou et al, 2020). With the recent advance described here, we could have performed more experiments in zebrafish and taken full advantage of this in vivo model for a mechanistic understanding of the genes of interest, such as mfn2.…”