TRPV1 Channels Are New Players in the Reticulum-Mitochondria Ca2+ Coupling in a Rat Cardiomyoblast Cell Line

Taxol-treatment alters endogenous TRPV1 expression and mitochondrial membrane potential in mesenchymal stem cells: Relevant in chemotherapy-induced pathophysiology

Microtubule-based chemotherapeutics, primarily Taxane-derived agents are still used as the major live-saving agents, yet have several side effects including serious loss of immune cells, bone density etc. which lowers the quality of life. This imposes the need to understand the effects of these agents on Mesenchymal Stem Cells (MSCs) in details. In this work we demonstrate that Taxol and Nocodazole affects the endogenous expression of TRPV1, a non-selective cation channel in MSCs. These agents also affect the status of polymerized Actin as well as Tyrosinated-tubulin, basal cytosolic Ca2+ and mitochondrial membrane potential (ΔΨm). Notably, pharmacological modulation of TRPV1 by Capsaicin or Capsazepine can also alter the above-mentioned parameters in a context-dependent manner. We suggest that endogenous expression of TRPV1 and pharmacological modulation of TRPV1 can be utilized to rescue some of these parameters effectively. These findings may have significance in the treatments and strategies with Microtubule-based chemotherapeutics and stem-cell based therapy.

Capsaicin-insensitivity of TRPV1-R575D mutant located at the lipid-water-interface region can be rescued by either extracellular Ca2+-chelation or cholesterol reduction

TRPV1 acts as a unique polymodal ion channel having distinct structure and gating properties. In this context, TRPV1-R575D represents a special mutant located at the inner lipid-water-interface (LWI) region that has less possibility of interaction with membrane cholesterol. In control conditions, this lab-generated mutant of TRPV1 shows no "ligand-sensitivity", reduced surface expression, reduced localization in the lipid rafts, yet induces high cellular lethality. Notably, the cellular lethality induced by TRPV1-R575D expression can be rescued by adding 5'I-RTX (a specific inhibitor of TRPV1) or by introducing another mutation in the next position, i.e. in TRPV1-R575D/D576R. In this work we characterized TRPV1-R575D and TRPV1-R575D/D576R mutants in different cellular conditions and compared with the TRPV1-WT. We report that the "ligand-insensitivity" of TRPV1-R575D can be rescued in certain conditions, such as by chelation of extracellular Ca2+, or by reduction of the membrane cholesterol. Here we show that Ca2+ plays an important role in the channel gating of TRPV1-WT as well as LWI mutants (TRPV1-R575D, TRPV1-R575D/D576R). However, chelation of intracellular Ca2+ or depletion of ER Ca2+ did not have a significant effect on the TRPV1-R575D. Certain properties related to channel gating of mutant TRPV1-R575D/D576R can be rescued partially or fully in a context -dependent manner. Cholesterol depletion also alters these properties. Our data suggests that lower intracellular basal Ca2+ acts as a pre-requisite for further opening of TRPV1-R575D. These findings enable better understanding of the structure-function relationship of TRPV1 and may be critical in comprehending the channelopathies induced by other homologous thermosensitive TRPVs.

10th European Calcium Society symposium: The Ca2+-signaling toolkit in cell function, health and disease

The 10th European Calcium Society symposium, organized in Leuven, Belgium on November 15-17, 2023, focused on the role of Ca2+ signaling in cell function, health and disease. The symposium featured six scientific sessions, 16 invited speakers - of whom two were postdoctoral researchers - and 14 short talks. The talks covered various aspects of intracellular Ca2+ signaling and its implications in pathology. Each session was opened by one or more invited speakers, followed by a series of presentations from speakers selected from submitted abstracts. Through short talks, poster presentations, awards, and sustainable travel fellowships, the symposium also fostered opportunities for the active participation of early-career researchers. At least half of the short talks were allocated to early-career researchers, thereby offering a platform for the presentation of ongoing work and unpublished results. Presentations were also broadcast in real-time for online attendees. In this Meeting Review, we aim to capture the spirit of the meeting and discuss the main take-home messages that emerged during the symposium.

So close, yet so far away: the relationship between MAM and cardiac disease

Mitochondria-associated membrane (MAM) serve as crucial contact sites between mitochondria and the endoplasmic reticulum (ER). Recent research has highlighted the significance of MAM, which serve as a platform for various protein molecules, in processes such as calcium signaling, ATP production, mitochondrial structure and function, and autophagy. Cardiac diseases caused by any reason can lead to changes in myocardial structure and function, significantly impacting human health. Notably, MAM exhibits various regulatory effects to maintain cellular balance in several cardiac diseases conditions, such as obesity, diabetes mellitus, and cardiotoxicity. MAM proteins independently or interact with their counterparts, forming essential tethers between the ER and mitochondria in cardiomyocytes. This review provides an overview of key MAM regulators, detailing their structure and functions. Additionally, it explores the connection between MAM and various cardiac injuries, suggesting that precise genetic, pharmacological, and physical regulation of MAM may be a promising strategy for preventing and treating heart failure.