Role of ezrin inhibitor in lysosomal morphology and dynamics

Gope, Anandita (2025) Role of ezrin inhibitor in lysosomal morphology and dynamics. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS Dissertation of Anandita Gope (20MS213)) 20MS213_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (1MB)

Abstract

Ezrin, a member of the ERM (ezrin–radixin–moesin) family, functions as a pivotal linker between the plasma membrane and the actin cytoskeleton, regulating cellular architecture and dynamics. When phosphorylated, ezrin undergoes conformational changes that determine its affinity for F-actin, thereby modulating the actin–membrane linkage and influencing cellular processes such as motility, endocytosis, and phagocytosis. Despite extensive studies on ezrin’s role at the cell cortex, its contribution to the endomembrane system, particularly lysosomes, remains underexplored. This study investigates the role of ezrin in regulating lysosomal morphology and dynamics. Specifically, we address the question: How does inhibition of ezrin activation affect the morphological and dynamical behaviour of lysosomes? The investigation centres around ezrin inhibition (EI) and its impact on lysosomal colocalization with phosphorylated ezrin (p-ezrin), lysosomal interactions, and the resulting consequences for lysosomal dynamics. Using confocal and super-resolution STED microscopy, we observed a marked decrease in colocalization between p-ezrin and lysosomes upon EI treatment, confirming that ezrin is a key regulator of actin association with lysosomes. Notably, morphological analyses revealed a significant increase in lysosomal size and eccentricity, indicating a transition towards more elongated and irregular (dumbbell-shaped) morphologies. Additionally, the area fraction of lysosomes increased without a corresponding rise in number density, suggesting morphological changes rather than proliferation. Mobility assays based on time-lapse imaging demonstrated a substantial reduction in lysosomal movement following EI treatment, accompanied by a noticeable increase in sustained interactions between lysosomal doublets. These findings imply impaired fission and/or fusion events, potentially disrupting lysosomal trafficking and dynamical behaviour.

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