When we talk about cells, we often refer to their most basic functions such as producing energy, creating proteins and reproducing through division. However, cells have a myriad of functions beyond the basics that are equally important in maintaining life. In this article, we will explore some of the lesser-known functions of cells.
The importance of cellular communication
Cells are not isolated entities; they communicate with each other to coordinate essential functions such as organ development, immune response and wound healing. One way cells communicate is through gap junctions. These are tiny channels that connect neighboring cells, allowing ions, nutrients and signaling molecules to pass through. Another way cells communicate is through extracellular vesicles. These are small structures that carry proteins, RNA and other molecules and can be released by cells to signal to other cells.
Intercellular signaling through gap junctions
Gap junctions are formed by protein channels called connexins, which form a hexagonal lattice between neighboring cells. These channels are gated, meaning that they can open or close depending on the cell’s needs. Gap junctions are critical for synchronizing the electrical activity of cardiac cells, coordinating contractions in smooth muscles and enabling immune cells to communicate during an infection.
Extracellular vesicles and their role in cell-to-cell communication
Extracellular vesicles (EVs) are small lipid bilayer structures that can be released by cells to the extracellular environment. There are three types of EVs: exosomes, which are formed by the inward budding of endosomal membranes, microvesicles, which are formed by the outward budding of plasma membranes, and apoptotic bodies, which are formed during cell death. EVs play important roles in intercellular communication by carrying proteins, nucleic acids, and lipids that influence the behavior and fate of recipient cells. They have been implicated in embryonic development, immune regulation, and cancer progression.
Cellular self-destruction: Apoptosis and autophagy
An important function of cells is to maintain the balance between growth and division and cell death. Apoptosis and autophagy are two forms of programmed cell death that are crucial for tissue remodeling, immune response, and eliminating damaged or abnormal cells.
Programmed cell death through apoptosis
Apoptosis is a highly regulated form of cell death that is characterized by fragmentation of the cell into apoptotic bodies, which are engulfed by phagocytes. Apoptosis is important for embryonic development, tissue homeostasis, and defense against infections. It can be triggered by a variety of internal or external stimuli such as DNA damage, oxidative stress, and cell signaling pathways. Apoptosis is tightly controlled by a network of proteins including caspases, BCL-2 family proteins, and tumor suppressor genes.
Self-digestion through autophagy
Autophagy is a cellular self-degradative process that removes damaged organelles and recycles cellular components. Autophagy is important for maintaining cellular homeostasis, sustaining energy during nutrient deprivation, and the elimination of intracellular bacteria and viruses. Autophagy can be induced by a variety of factors such as nutrient deprivation, oxidative stress, and protein misfolding. Autophagy is regulated by a complex network of proteins such as ATG proteins, mTOR, and Beclin-1.
Mitochondria- Beyond energy production
Mitochondria are organelles that are often referred to as the ‘powerhouses of the cell’ because they produce energy through oxidative phosphorylation. However, mitochondria perform many other critical functions outside of energy production that are essential for cellular homeostasis and survival.
Mitochondria and calcium signaling
Mitochondria play a critical role in regulating cellular calcium signaling. Calcium is a ubiquitous signaling molecule that regulates a wide range of cellular functions such as cell proliferation, gene expression, and apoptosis. The concentration of calcium ions is tightly regulated by a network of channels and pumps. Mitochondria act as a calcium sink by taking up and releasing calcium ions in response to cellular signaling. This is important for modulating the amplitude and duration of calcium signals and regulating cellular metabolism and cytoskeletal dynamics.
Mitochondria and apoptosis
Mitochondria also play a critical role in regulating apoptosis. They release pro-apoptotic proteins such as cytochrome c into the cytoplasm when triggered by cellular stress, inducing programmed cell death. This is regulated by the balance between pro- and anti-apoptotic BCL-2 family proteins and is affected by cellular stress signaling pathways such as DNA damage and oxidative stress.
Conclusion
Cells are complex entities that perform a multitude of functions beyond the basics. They communicate with each other, self-destruct when required and are regulated by multiple intracellular mechanisms. Further research into these cellular functions will lead to a better understanding of fundamental biological processes and the development of novel therapies for disease.
- What are extracellular vesicles?
- What is the function of mitochondria?
- What is apoptosis?
- What is autophagy?
- What regulates intracellular calcium signaling?
- What is the role of mitochondria in regulating apoptosis?
References
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- Jin, M., & Klionsky, D. J. (2014). Regulation of autophagy: Modulation of the physiology of the cell. Molecular cell, 56(5), 550-566.
- Kroemer, G., Galluzzi, L., & Brenner, C. (2007). Mitochondrial membrane permeabilization in cell death. Physiological reviews, 87(1), 99-163.
- Sade, H., Krishna, S., & Sarin, A. (2017). Gap junctions and their role in embryonic and adult stem cell proliferation and differentiation. Journal of cell communication and signaling, 11(1), 53-71.
- van Niel, G., D’Angelo, G., & Raposo, G. (2018). Shedding light on the cell biology of extracellular vesicles. Nature reviews. Molecular cell biology, 19(4), 213-228.