Chamberlain, J. | bioRxiv Science

bioRxiv2023

Enveloped viruses pseudotyped with mammalian myogenic cell fusogens target skeletal muscle for gene delivery

Entry of enveloped viruses into cells is mediated by fusogenic proteins that form a complex between membranes to drive rearrangements needed for fusion. Skeletal muscle development also requires membrane fusion events between progenitor cells to form multinucleated myofibers. Myomaker and Myomerger are muscle-specific cell fusogens, but do not structurally or functionally resemble classical viral fusogens. We asked if the muscle fusogens could functionally substitute for viral fusogens, despite their structural distinctiveness, and fuse viruses to cells. We report that engineering of Myomaker and Myomerger on the membrane of enveloped viruses leads to specific transduction of skeletal muscle. We also demonstrate that locally and systemically injected virions pseudotyped with the muscle fusogens can deliver micro-Dystrophin (Dys) to skeletal muscle of a mouse model of Duchenne muscular dystrophy. Through harnessing the intrinsic properties of myogenic membranes, we establish a platform for delivery of therapeutic material to skeletal muscle.

cell biology↗

bioRxiv2022

Blockade of redox second messengers inhibits JAK/STAT and MEK/ERK signaling sensitizing FLT3-mutant acute myeloid leukemia to targeted therapies

FLT3-mutations are diagnosed in 25-30% of patients with acute myeloid leukemia (AML) and are associated with a poor prognosis. AML is associated with the overproduction of reactive oxygen species (ROS), which drives genomic instability through the oxidation of DNA bases, promoting clonal evolution, treatment resistance and poor outcomes. ROS are also important second messengers, triggering cysteine oxidation in redox sensitive signaling proteins, however, the specific pathways influenced by ROS in AML remain enigmatic. Here we have surveyed the posttranslational architecture of primary AML patient samples and assessed oncogenic second messenger signaling. Signaling proteins responsible for growth and proliferation were differentially oxidized and phosphorylated between patient subtypes either harboring recuring mutation in FLT3 compared to patients expressing the wildtype-FLT3 receptor, particularly those mapping to the Src family kinases (SFKs). Patients harboring FLT3-mutations also showed increased oxidative posttranslational modifications in the GTPase Rac activated-NADPH oxidase-2 (NOX2) complex to drive autocratic ROS production. Pharmacological and molecular inhibition of NOX2 was cytotoxic specifically to FLT3-mutant AMLs, and reduced phosphorylation of the critical hematopoietic transcription factor STAT5 and MAPK/ERK to synergistically increase sensitivity to FLT3-inhibitors. NOX2 inhibition also reduced phosphorylation and cysteine oxidation of FLT3 in patient derived xenograft mouse models in vivo, highlighting an important link between oxidative stress and oncogenic signaling. Together, these data raise the promising possibility of targeting NOX2 in combination with FLT3-inhibitors to improve treatment of FLT3-mutant AML. One Sentence SummaryFLT3-precision therapies have entered the clinic for AML however, their durability is limited. Here we identify the Rac-NOX2 complex as the major driver of redox second messenger signaling in FLT3-mutant AML. Molecular and pharmacological inhibition of NOX2 decreased FLT3, STAT5 and MEK/ERK signaling to delay leukemia progression, and synergistically combined with FLT3 inhibitors.

cancer biology↗