Background Information

Throughout the discipline of biology, no one truly knows the importance of inorganic
phosphate and the roles it plays in phospholipid structures and cellular metabolism. Inorganic
phosphate has many essential responsibilities including the building of cell membranes and the process of cellular metabolism. Turns out that a guy by the name of Justus von Liebig discovered that inorganic phosphate was proven to be required by plants in order for them grow. This discovery resulted in the development of fertilizer which includes nitrogen, potassium, and phosphate. Looking deeper into the reasons that inorganic phosphate aids in cellular metabolism is that it regulates postprandial glucose storage and controls the distribution and supply of the energy to the brain and muscles1. The way that phosphate is part of glucose storage the supply of energy is because of its appearance in phospholipids. Phospholipid structures are parts of the cell membrane that consists of two fatty acids and a phosphate group that are attached to a glycerol backbone2. These structures are used in plasma membrane within cells and aid in controlling what comes in and out of the cell. Because of the chemical and physical properties of a phospholipid, the lipid bilayer of the membrane can allow solutes to easily pass through, which is essential for cell metabolism. In addition, the phosphate group in the phospholipid group can be attached to other organic molecules to form different type of phospholipid4. These different phospholipids compositions can allow the cell to make changes to its membrane, usually in a response to changing environment conditions.

Multilamellar organelles on the other hand showcase the versatility of phospholipids. Multilamellar organelles are composed of many layers of phospholipids, and they reside within the plasma cell membrane and aid in the secretion within the membrane and aid in the storage of lipids3. These organelles are found in different types of cells and provide a diverse set of functions for each type of cell they are in and the environment they reside. As an example, in skin cells the multilamellar organelles secrete lipids to maintain a water barrier, denying water from being absorbed by the skin in a response to liquid environment. While also allowing sweat to secrete out of the skin in a response to hot or humid environment. Overall, inorganic phosphate has a big responsibility, from the control of energy metabolism to the development of the cell membrane. The roles of phosphate are as diverse as they are important because of the adaptation to new environment. The same goes for phospholipids and multilamellar organelles, both the phospholipid bilayer and multilamellar organelles rely on the use of inorganic phosphate for their daily functions. Each with their own set of unique functions aid in the survival of the cellular organism. Insights into how inorganic phosphate functions and the use of it in phospholipids and multilamellar organelles can help aid in the development of new drugs and therapies. Understanding what helps a new medication be absorbed quicker into the cells of an organism can decrease the time needed for the medication to take effect. Essential speeding up the process it takes to fight an illness or the cure of a disease. In the end, inorganic phosphate plays a major role in living organisms and has the potential to find new progress in medical science.

Data Analysis

One of the most essential molecules for life is inorganic phosphate and not much is very known about this molecule within animal tissue. A group of ten scientists conducted an experiment to see how phosphate sensing organelles, like PXo bodies, regulate phosphate levels in a cell and aid in tissue homeostasis. While the article itself goes into great detail about the how the experiment was conducted, what was resulted from the experiment, and how that information can be used so future scientists can finally understand more about inorganic phosphate.

Throughout the scientific analysis done on phosphate sensing organelles, there are images provided for the reader to get an understanding of what was occurring during the experiments. In the second figure on the article, there are mini images that are taken of PXo bodies using florescent lighting and dyes to identify different parts of the cell. The basic shape of the PXo bodies in the images are circular shaped, however not a perfect circle. When going through the seven sets of mini images on figure two, four of the seven sets came back with having yellow in the florescence image. These four were LysoT, lipids, glycosylation, and phospholipids, meaning that the PXo bodies observed have an association with each of the listed areas of the cell. The three that are not associated with PXo bodies are lysosomes, the Golgi, and endocytosis.

Moving on to the next figure in the article, figure three shows the reader how the PXo bodies regulate inorganic phosphate in the cytoplasm. The scientists conducting the experiment used a FLIPPi sensor to take images of the intracellular inorganic phosphate while the PXo bodies are being reduced in the protein. These images would show the fluorescence resonance energy transfer (fret) in the protein and would display if there are high amounts or low amounts of inorganic phosphate in the cytoplasm. When PXo is inhibited, there are an increase in inorganic phosphate in the cytoplasm. This means that PXo can be used to regulate the levels of inorganic phosphate by either increasing the amount of PXo bodies or inhibiting the amount of PXo bodies in the cytoplasm.

Looking at the PXo bodies and their formations, figure four provides images of normal looking PXo bodies, PXo with different types of inhibitors, and the PXo when inorganic phosphate is added. The two main characteristics of the PXo bodies when a phosphonoformic acid, inhibitor, is introduced, is that the PXo bodies are decreasing in size and in the amount of them in the cell. On the other hand, when a supplemental amount of inorganic phosphate is added to the cell, it would have the opposite effect, with an increase in size and increase in the amount of them in the cell. This would mean that the formation of the PXo bodies depend on the availability of inorganic phosphate.

The final image that will be discussed is figure five, where pie charts were put together to show the number of phospholipids found within the PXo bodies normally verses when an inhibitor is added. When the same phosphonoformic acid inhibitor is added to the PXo body, the total number of phospholipids decreased. Another thing that can be seen in the pie charts is that the inhibitor also changed the overall composition of the different types of phospholipids in the PXo body. For instance, phosphatidylcholine normally took up 45% of the total phospholipids in the PXo body but decreased to only 39%. While some types of phospholipids change, a couple of them remain the same percent composition, like phosphatidylethanolamine

After analyzing the article, it can be concluded that the data from the experiment supports the idea that PXo bodies form distinct organelles with a unique biochemical function in the cell. This is because the PXo has shown that it is capable of regulating the amount of inorganic phosphate in the cytoplasm, figure three. It can also be understood that PXo bodies also rely on inorganic phosphate to operate at a normal size and quantity, limiting the inorganic phosphate would restrict the PXo functions in the cell.

Reference
Xu C., Xu J., Tang HW., Ericsson M., Weng JH., DiRusso J., Hu Y., Ma W., Asara J., Perrimon
N. A phosphate-sensing organelle regulates phosphate and tissue homeostasis. Nature.
2023; 617: 798-806

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Multilamellar Bodies via Autophagy. Mol Biol Cell. 2000; 11: 255-268.
4. Anon. Lipid Molecules – Phospholipids. 2023; LibreTexts Biology,
https://bio.libretexts.org/@go/page/12691