VAP-B AND ITS ROLE IN AMYOTROPHIC LATERAL SCLEROSIS
The VAPs (VAMP-associated proteins) are highly conserved integral endoplasmic reticulum (ER)-membrane proteins, implicated in diverse cellular functions, including regulation of lipid transport and homeostasis, membrane trafficking, neurotransmitter release, stabilization of presynaptic microtubules, and the unfolded protein response (UPR).
A single missense mutation within the human VAP-B gene was identified in three forms of the familial motor-neuron disease (MND) including amyotrophic lateral sclerosis (ALS). The mutation substitutes a highly conserved proline residue at position 56 with a serine (P56S) and causes motor-neuron degeneration by an as-yet-unknown mechanism. Prof. Sima Lev and her team discovered that the P56S mutation induces conformational changes in VAP-B, which facilitates its aggregation and consequently inhibits its physiological function.
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REGULATION OF MEMBRANE TRAFFICKING BY NON-VESICULAR TRANSPORT MECHANISMS
Membrane trafficking pathways are mediated by a network of proteins and lipids that coordinately function to efficiently and rapidly transport lipids, secreted, luminal and integral membrane proteins to their final cellular destinations.
The tight regulation of membrane transport events is not only fascinating but also fundamental for normal cell function and survival. Membrane trafficking events are mediated by both vesicular and non-vesicular transport mechanisms.
While vesicular transport is involved in the transport of both proteins and lipids, non-vesicular transport is involved in lipid transport and is mainly mediated by various intracellular lipid-transfer proteins (LTPs). Prof. Sima Lev and her team had a remarkable contribution to the field of lipid-transport and the interplay between intracellular lipid transport and membrane trafficking events.
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THE ROLE OF NIR PROTEINS IN PHOSPHATIDYLINOSITOL (PI) TRANSPORT AND BEYOND
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REGULATIO OF GOLGI STRUCTURE AND FUNCTION IN INTERPHASE AND MITOTIC CELLS
The Golgi apparatus (discovered by Camillo Golgi), is the central organelle of the secretory pathway, involved in the post-translational modification of many cellular proteins and lipids and their sorting to appropriate subcellular destinations. Maintenance of the structural integrity of the Golgi apparatus is critical for its secretory function and is largely dependent on membrane trafficking events. Prof. Sima Lev showed that the lipid-transfer protein Nir2 is required for maintenance the structure of the Golgi in interphase by regulating the lipid composition of this organelle.
During mitosis, the Golgi apparatus is extensively fragmented into thousands of vesicles and tubules. These morphological changes coincide with the blockage of membrane transport to and through the Golgi apparatus. Late in mitosis, however, the Golgi reassembles and membrane trafficking events are concomitantly restored. Interestingly, Prof. Lev found that Nir2 is extensively phosphorylated during mitosis and regulates cytokinesis progression.
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