Biology subjects

Sadi, A.

Publications and source records attributed to Sadi, A..

3 recordsLinked to original sources

bioRxiv2026

Hippocampal Projections to the Striatal Compartments, Striosome and Matrix, are Spatially Segregated in CA1

The hippocampus routes information to the striatum through at least four polysynaptic circuits. Striatal projection neurons are organized into two tissue compartments, the matrix and striosome, which differ in their embryologic origins, relative abundance, intra-striate location, and afferent and efferent connectivity. These compartments are embedded in distinct functional networks and are activated by different tasks. Consequently, hippocampal inputs that route preferentially through the striosome may underpin different functions and engage with different remote networks than inputs that route through the matrix. It was unknown whether striosome-bound and matrix-bound projections from the hippocampus followed different polysynaptic circuits. We assessed hippocampo-striate projections in living humans using probabilistic diffusion tractography by first parcellating the striatum into voxels with striosome-like and matrix-like structural connectivity. We then quantified structural connectivity between hippocampal efferents (CA1) to each set of compartment-like voxels. CA1 projections to striosome-like voxels in the dorsal striatum (caudate and putamen) were 3.1-fold more abundant than those to matrix-like voxels, particularly in caudo-lateral CA1. This striosome-favoring bias was similar in three segregated hippocampo-striate circuits, in streamlines routing through the subiculum, lateral septum, or medial prefrontal cortex. However, a small region in rostro-medial CA1 preferentially targeted matrix-like voxels. Functional connectivity between CA1 and compartment-like voxels matched this segregated pattern: CA1 activation was correlated with striosome-like voxels but anti-correlated with matrix-like voxels. Additionally, streamlines from CA1 to nucleus accumbens exhibited hemispheric asymmetries, with the left hemisphere biased towards matrix and the right towards striosome. These findings suggest that hippocampo-striate projections are spatially segregated into compartment-specific circuits.

neuroscience↗

bioRxiv2024

The multifunction Coxiella effector Vice stimulates macropinocytosis and interferes with the ESCRT machinery

Intracellular bacterial pathogens divert multiple cellular pathways to establish their niche and persist inside their host. Coxiella burnetii, the causative agent of Q fever, secretes bacterial effector proteins via its Type 4 secretion system to generate a Coxiella-containing vacuole (CCV). Manipulation of lipid and protein trafficking by these effectors is essential for bacterial replication and virulence. Here, we have characterized the lipid composition of CCVs and discovered that the effector Vice interacts with phosphoinositides and membranes enriched in phosphatidylserine (PS) and lysobisphosphatidic acid (LBPA). Remarkably, eukaryotic cells ectopically expressing Vice present compartments that resemble early CCVs in both morphology and composition. We discovered that the biogenesis of these compartments relies on the double function of Vice. The effector protein initially localizes at the plasma membrane of eukaryotic cells where it triggers the internalization of large vacuoles by macropinocytosis. Then, Vice stabilizes these compartments by perturbing the ESCRT machinery and inhibiting the formation of intraluminal vesicles (ILVs). Collectively, our results reveal that Vice is an essential C. burnetii effector protein capable of hijacking two major cellular pathways to shape the bacterial replicative niche. Significance statementCoxiella burnetii is a unique bacterial pathogen that secretes more than a hundred effector proteins to manipulate cellular processes and establish a replicative niche, the Coxiella-containing vacuole (CCV). Our study identified host cell lipids that are actively recruited by the bacterium to the CCV. Using a library of effector mutants, we identified the protein Vice (for Vacuole-inducing Coxiella effector) as the first bacterial effector capable of interacting with lysobisphosphatydic acid-enriched membranes and accumulating this lipid to CCVs. We show that Vice is also capable of stimulating macropinocytosis and inhibiting the ESCRT machinery. Together, our data show how a single bacterial effector can manipulate different cellular processes to favor the biogenesis of a bacterial pathogens niche.

microbiology↗

bioRxiv2023

The novel bacterial effector protein CbEPF1 mediates ER-LD membrane contacts to regulate host lipid droplet metabolism

Effective intracellular communication between cellular organelles is pivotal for maintaining cellular homeostasis. Tether proteins, which are responsible for establishing membrane contact sites between cell organelles, enable direct communication between organelles and ultimately influence organelle function and host cell homeostasis. While recent research has identified tether proteins in several bacterial pathogens, their functions have predominantly been associated with mediating inter-organelle communication specifically between the bacteria containing vacuole (BCV) and the host endoplasmic reticulum (ER). However, this study reveals a novel bacterial effector protein, CbEPF1, which acts as a molecular tether beyond the confines of the BCV and facilitates interactions between host cell organelles. Coxiella burnetii, an obligate intracellular bacterial pathogen, encodes the FFAT motif-containing protein CbEPF1 which localizes to host lipid droplets (LDs). CbEPF1 establishes inter-organelle contact sites between host LDs and the ER through its interactions with VAP family proteins. Intriguingly, CbEPF1 modulates growth of host LDs in a FFAT motif-dependent manner. These findings highlight the potential for bacterial effector proteins to impact host cellular homeostasis by manipulating inter-organelle communication beyond conventional BCVs.

cell biology↗