Role of Gap Junction Protein Connexin 43 and Golgi Apparatus in Cell Migration in Cancer Cells

Mukherjee, Suvam (2023) Role of Gap Junction Protein Connexin 43 and Golgi Apparatus in Cell Migration in Cancer Cells. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (PhD thesis of Suvam Mukherjee (15IP020)) 15IP020.pdf - Submitted Version Restricted to Repository staff only Download (3MB)

Abstract

Cell migration is a fundamental process in biology and vital for maintaining organismal homeostasis. It is tightly regulated and plays a crucial role in tissue regeneration as well as metastatic dissemination of tumour cells in various cancers. For effective migration, cells remodel various organelles to facilitate the process. The Golgi apparatus serves as a signalling hub and is believed to direct secretory trafficking, increase membrane delivery at the leading edge and potentially directional cell migration. However, conflicting results on the orientation of the Golgi relative to the migrating cell, raise questions about its regulation. In order to understand its regulation, herein, we address the role of gap junction protein Connexin 43 which connects cells and have been demonstrated to require microtubules to maintain their plasma membrane distribution. We utilize HeLa (wild type) and HeLa 43 cells and report that the connection of neighbouring cells by functional Connexin 43 channels (in HeLa 43) affects Golgi morphology, as seen on treatment with Brefeldin A. It also reduces the ability of re-orientation of Golgi (towards the leading edge) on triggering cell migration in cancer cells. The orientation of Golgi is correlated to the distance of the cell centre from the wound edge in the absence of Connexin 43 but the correlation is lost in HeLa 43. Expression of Connexin 43 also reduces migration velocity but the front displays a more coherent movement. Vimentin overexpression in HeLa 43 supports the role of Connexin 43 in altering the nature of cell migration to more collective. Basal actin too is significantly higher. Together, the data shows that Connexin 43 expression alters the cytoskeleton. To understand if the altered cytoskeleton alters the mechanical state of the membrane, parallelly, membrane fluctuations and tension were checked. HeLa 43 has a lower membrane tension and a more uniform intracellular distribution in comparison to HeLa. This helps us propose that the reduced Golgi reorientation in HeLa 43 may be linked to a lesser need for directed secretory trafficking. Since it is believed to be required to buffer the increasing tension. We have also parallelly observed a similar effect of Connexin 43 on migration in glioma cell lines as presented in this study. Therefore, we demonstrate that the presence of a previously unexplored axis of control of Golgi distribution, besides cytoskeleton, is by Connexin 43.

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