Biology subjects

Eisen, J. N.

Publications and source records attributed to Eisen, J. N..

3 recordsLinked to original sources

bioRxiv2025

Multiple interactions mediate the localization of BLTP2 at ER-PM contacts to control plasma membrane dynamics

BLTP2/KIAA0100, a bridge-like lipid transfer protein, was reported to localize at contacts of the endoplasmic reticulum (ER) with either the plasma membrane (PM) or recycling tubular endosomes depending on the cell type. Our findings suggest that mediating bulk lipid transport between the ER and the PM is a key function of this protein as BLTP2 tethers the ER to tubular endosomes only after they become continuous with the PM and that it also tethers the ER to macropinosomes in the process of fusing with the PM. We further identify interactions underlying binding of BLTP2 to the PM, including phosphoinositides, the adaptor proteins FAM102A and FAM102B, and also N-BAR domain proteins at membrane-connected tubules. The absence of BLTP2 results in the accumulation of intracellular vacuoles, many of which are connected to the plasma membrane, pointing to a role of the lipid transport function of BLTP2 in the control of PM dynamics.

cell biology↗

bioRxiv2022

A partnership of the lipid scramblase XK and of the lipid transfer protein VPS13A at the plasma membrane

Chorea-acanthocytosis and McLeod syndrome are diseases with shared clinical manifestations caused by mutations in VPS13A and XK, respectively. Key features of these conditions are the degeneration of caudate neurons and the presence of abnormally shaped erythrocytes. XK belongs to a family of plasma membrane (PM) lipid scramblases whose action results in exposure of PtdSer at the cell surface. VPS13A is an ER-anchored lipid transfer protein with a putative role in the transport of lipids at contacts of the ER with other membranes. Recently VPS13A and XK were reported to interact by still unknown mechanisms. So far, however, there is no evidence for a colocalization of the two proteins at contacts of the ER with the PM, where XK resides, as VPS13A was shown to be localized at contacts between the ER and either mitochondria or lipid droplets. Here we show that VPS13A can also localize at ER-PM contacts via the binding of its PH domain to a cytosolic loop of XK, that such interaction is regulated by an intramolecular interaction within XK and that both VPS13A and XK are highly expressed in the caudate neurons. Binding of the PH domain of VPS13A to XK is competitive with its binding to intracellular membranes that mediate other tethering functions of VPS13A. Our findings support a model according to which VPS13A-dependent lipid transfer between the ER and the PM is coupled to lipid scrambling within the PM. They raise the possibility that defective cell surface exposure of PtdSer may be responsible for neurodegeneration.

cell biology↗

bioRxiv2020

α-Synuclein-112 impairs synaptic vesicle recycling consistent with its enhanced membrane binding properties

Synucleinopathies are neurological disorders associated with -synuclein overexpression and aggregation. While it is well established that overexpression of wild type -synuclein (-syn-140) leads to cellular toxicity and neurodegeneration, much less is known about other naturally occurring -synuclein splice isoforms. In this study we provide the first detailed examination of the synaptic effects caused by one of these splice isoforms, -synuclein-112 (-syn-112). -Syn-112 is produced by an in-frame excision of exon 5, resulting in deletion of amino acids 103-130 in the C-terminal region. -Syn-112 is upregulated in the substantia nigra, frontal cortex, and cerebellum of parkinsonian brains and is correlated with susceptibility to sporadic Parkinsons disease (PD), dementia with Lewy bodies (DLB) and multiple systems atrophy (MSA). We report here that -syn-112 binds strongly to anionic phospholipids when presented in highly-curved liposomes, similar to -syn-140. However, -syn-112 bound significantly stronger to all phospholipids tested, including the phosphoinositides. -Syn-112 also dimerized and trimerized on isolated synaptic membranes, while -syn-140 remained largely monomeric. When introduced acutely to lamprey synapses, -syn-112 robustly inhibited synaptic vesicle recycling. Interestingly, -syn-112 produced effects on the plasma membrane and clathrin-mediated synaptic vesicle endocytosis that were phenotypically intermediate between those caused by monomeric and dimeric -syn-140. These findings indicate that -syn-112 exhibits enhanced phospholipid binding and oligomerization in vitro and consequently interferes with synaptic vesicle recycling in vivo in ways that are consistent with its biochemical properties. This study provides additional evidence suggesting that impaired vesicle endocytosis is a cellular target of excess -synuclein and advances our understanding of potential mechanisms underlying disease pathogenesis in the synucleinopathies.

neuroscience↗