Biology subjects

Murphy, C. S.

Publications and source records attributed to Murphy, C. S..

3 recordsLinked to original sources

bioRxiv2026

Host CD59 Potentiates the Type III Secretion System in Yersinia pseudotuberculosis

Type III secretion systems (T3SS) play critical roles in disease for many Gram-negative pathogens. Although the structural details of T3SS assembly have been extensively studied, the intimate interactions between T3SS components and the target host plasma membrane are poorly characterized. A previous RNA interference (RNAi) study identified the GPI-linked surface protein CD59 as a critical host component that supports the movement of Yersinia pseudotuberculosis (Yptb) T3SS effectors into the host cytosol. We show here that both depletion and increased levels of CD59 reduced Yptb T3SS pore formation and Yop translocation into host target cells. CD59 is unlikely to act as a receptor for the T3SS translocon, as physical blockade of CD59 or enzymatic removal of all GPI-linked surface proteins had no effect on T3SS function. Consistent with its importance in supporting T3SS function, efficient bacterial effector-mediated focal adhesion disassembly was dependent on CD59. Surprisingly, depletion of CD59 interfered with the rearrangement of the lipid raft marker GM1 that occurs after Yptb adhesion to host cells, indicating that CD59 supports lipid microdomain dynamics. Consistent with a role in modulating lipid composition, the loss of CD59 led to the accumulation of phosphatidylcholine and alterations in both fatty acid chain lengths and saturation levels. This work points to a role for CD59 in maintaining plasma membrane dynamics necessary for efficient T3SS translocon function. In addition, a polarization index is described that quantifies the asymmetric association of membrane compartments with organelles.

microbiology↗

bioRxiv2024

Inhibition of Acyl-CoA Synthetase Long Chain Isozymes Decreases Multiple Myeloma Cell Proliferation and Causes Mitochondrial Dysfunction

Multiple myeloma (MM) is an incurable cancer of plasma cells with a 5-year survival rate of 59%. Dysregulation of fatty acid (FA) metabolism is associated with MM development and progression; however, the underlying mechanisms remain unclear. Acyl-CoA synthetase long-chain family members (ACSLs) convert free long-chain fatty acids into fatty acyl-CoA esters and play key roles in catabolic and anabolic fatty acid metabolism. The Cancer Dependency Map data suggested that ACSL3 and ACSL4 were among the top 25% Hallmark Fatty Acid Metabolism genes that support MM fitness. Here, we show that inhibition of ACSLs in human myeloma cell lines using the pharmacological inhibitor Triascin C (TriC) causes apoptosis and decreases proliferation in a dose- and time-dependent manner. RNA-seq of MM.1S cells treated with TriC for 24 h showed a significant enrichment in apoptosis, ferroptosis, and ER stress. Proteomics of MM.1S cells treated with TriC for 48 h revealed that mitochondrial dysfunction and oxidative phosphorylation were significantly enriched pathways of interest, consistent with our observations of decreased mitochondrial membrane potential and increased mitochondrial superoxide levels. Interestingly, MM.1S cells treated with TriC for 24 h also showed decreased mitochondrial ATP production rates and overall lower cellular respiration. ImplicationsOverall, our data support the hypothesis that suppression of ACSL in human MM cells inhibit their growth and viability, indicating that ACSL proteins may be promising therapeutic targets in treating myeloma progression.

cancer biology↗

bioRxiv2022

The Fatty Acid Binding Protein Family Represents a Novel Target in Multiple Myeloma

BackgroundMultiple myeloma is an incurable plasma cell malignancy with only a 53% 5-year survival rate, highlighting a critical need for new multiple myeloma vulnerabilities and therapeutic avenues. Herein, we explored a novel multiple myeloma target: the fatty acid binding protein (FABP) family. MethodsMyeloma cells treated with FABP inhibitors (BMS3094013 and SBFI-26) were examined in vivo and in vitro for cell cycle, proliferation, apoptosis, mitochondrial membrane potential, cellular metabolism (oxygen consumption rates and fatty acid oxidation), and DNA methylation. Myeloma cell responses to BMS309403 and/or SBFI-26 were assessed with RNA-sequencing and proteomic analysis, and confirmed with western blotting and qRT-PCR. Myeloma cell dependency on FABPs was assessed using DepMap. Finally, MM patient datasets (CoMMpass and GEO) were mined for FABP expression correlations with clinical outcomes. ResultsMyeloma cells treated with FABPi or with FABP5 knockout (generated via CRISPR/Cas9 editing) exhibited diminished proliferation in vitro. FABPi had potent anti- tumor effects both in vitro and in vivo in two pre-clinical MM mouse models where increased mouse survival was observed. FABPi negatively impacted mitochondrial respiration and reduced expression of MYC and other key signaling pathways in MM cells. Clinical data demonstrated worse overall and progression-free survival in patients with high FABP5. ConclusionsThis study establishes the FABP family as a therapeutically actionable dependency in multiple myeloma with a multitude of actions and cellular roles that result in the support of myeloma progression. Statement of translational relevanceMultiple myeloma (MM) is an incurable disease of the plasma cell and MM patients require better treatments as soon as possible. The fatty acid binding protein (FABP) family plays a number of roles in cells, including supporting fatty acid oxidation, lipid shuttling and signal transduction. Here, we demonstrate with CoMMpass and other clinical data that FABPs represent a biomarker for aggressive disease in MM, and are a novel, targetable protein family expressed by myeloma cells. Pharmacologically inhibiting FABPs kills tumor cells and induces cell cycle arrest in vitro and in pre-clinical models. Mechanisms of action are multitudinous, as we discovered with RNA-sequencing, proteomic analysis, and phenotyping assays. Cell metabolism, cell signaling, cell stress, and epigenetic signatures were altered in MM cells when FABPs were inhibited. In summary, targeting FABP5 holds great therapeutic potential for killing diseased cells, with few negative off-target effects on healthy cells.

cancer biology↗