Scientific Literacy Essay – Final
This paper will be used to delve deeper into the scientific research paper of “Defining the role of cytoskeletal components in formation of apoptopodia and apoptotic bodies during apoptosis” which was created on September 5th of 2019. In this paper the methods, discussions, and the results of the paper will be discussed as well as covering the topics and how they could be used for future research.
Apoptosis is the programmed cell death that occurs normally in order for an organism to grow and develop. During apoptosis, cells change into fragments of these dying cells that are known as apoptotic bodies (ApoBDs). Data from this specific article states that apoptopodia is a beginner type cellular membrane extension (known as membrane protrusion) that has the ability to form if actin polymerisation and microtubule assembly (Caruse et al., 2019). Cytoskeletal components are cells made up of microtubules, actin filaments, and intermediate filaments. In this article all of these components are used to define the role of these cytoskeletal components being used to form apoptopodia and apoptotic bodies during apoptosis.
There are a multitude of methods used in this detailed study, with a few being cell culture research, isolation of primary mouse monocytes and thymocytes, induction of apoptosis, DIC and fluorescence microscopy, 3D culture imaging, and ATP release essay (Caruso et al, 2019). The cytoskeletal components are also said to have some variation in terms of the morphology, function, and regulation and are generated by resting cells and activated cells. While these components are found in the beginning of apoptosis, it is unknown whether or not it is also involved in the morphological changes that are found in the later stages of apoptosis. These morphological changes include the shrinkage of the cell, fragmentation into the membrane bound apoptotic bodies (ApoBDs), and it is also in the rapid phagocytosis by neighboring cells. Phagocytosis is where the cells engulf large particles that are greater than 0.5 micrometers (D’Herde 2018).
This research group monitored the progression of apoptosis by confocal microscopy (Caruso et al., 2019) and focused primarily on the apoptopodia step. Confocal microscopy is a camera that uses light from a laser through a standard light microscope to excite the specimen (in this case, the apoptotic bodies) within a sharp focused plane. As seen in Figure 2, in parts A, C, E, and F, the pictures represent different cells per image, and the percentage of apoptopodia in SiR-actin(high) and SiR-actin(low). These images were specifically taken with confocal microscopy at ten micrometers per image. Figure A provides insight into ROCK I Jurkat T cells that are covered with SiR-actin fluorescent probes. The results from this specific image revealed that there was a high percentage of SiR-actin staining (SiR-actin high). Figure C contains apoptotic THP-1 monocytes that are also stained in SiR-actin and CD45-FITC (which indicates the plasma membrane). This revealed that the percentage of SiR-actin high and low were almost at equal percentages, with SiR-actin high being about 10 percent higher. The other figures also contained almost equal amounts of SiR-actin high, with Figure E containing apoptotic primary mouse thymocytes and Figure F composed of primary mouse CD14+ monocytes. These images described the importance of the role of actin polymerisation in apoptotic membrane protrusion formation (Caruso et al, 2019).
An interesting reference they used for the ROCK I, which is the research paper by M Sebbagh named, “Caspase-3-mediated cleavage of ROCK I induces MLC phosphorylation and apoptotic membrane blebbing” mentions the topic of the activation of caspases during the execution phase that occurs in apoptosis which causes proteolytic cleavage in multiple substrates. This can cause problems with the phenotype of the apoptotic cells. ROCK I is cleaved by the caspase-3 at a specific sequence, which removes its carboxy-terminal domain, which irregulates the kinase activity. ROCK I cleavage is increased as well as phosphorylated MLC in apoptotic cells that are located in ROCK I proteins (Sebbagh et al, 2001). The phosphorylation combined with the membrane blebbing, which is a bulge in the plasma membrane caused by uncoupling of the cytoskeleton within the membrane, is repelled by the stopping of ROCK proteins. The study came to the conclusion that ROCK I being activated by caspase-3 was responsible for bleb formation in apoptotic cells.
While researching the specific step of the apoptopodia, they discovered that actin polymerisation was nonessential for its formation (Caruso et al, 2019). While focusing on this step as well, they noted the presence of F-actin and microtubules that were made by T cells and monocytes. These F-actin are actin microfilaments in the cytoskeleton of these apoptotic cells. The results from looking at this specific step was discovering that T cells and monocytes form apoptotic membrane protrusions in cell suspension, as well as in 3D cultures (Caruso et al, 2019). Though this was discovered, it was still unclear as to whether apoptopodia possess physical characteristics to mimic these cultures, as such with other cell membrane protrusions. It is then mentioned of the role of the F-actin in this protrusion formation, and if it is actually involved in the formation of the apoptopodia. Different cells and monocytes are used for the specific purpose of seeing if these cells produced protrusions containing F-actin (Caruso et al, 2019).
It was also found that targeting actin polymerization and microtubule assembly pharmacologically had no major effect on apoptopodia formation (Caruso et al, 2019). This adds on interestingly due to the fact that the reduction in vimentin expression did not affect the formation of apoptotic membrane protrusions either (Caruso et al, 2019). Vimentin is known as an intermediate filament component that plays a role in cellular protrusions.
These findings helped add new information to the scientific community and will further help the research of the role of cytoskeletal components. Since microtubules are in around ninety percent of apoptotic membrane protrusions, they could be an important tool in future apoptotic findings. Cancer findings could be a major investment with this research, specifically being able to control apoptosis to have the ability to target the cancerous cells and destroy them, leaving the healthy and normal cells to flourish.
Works Cited
Caruso, S., Atkin-Smith, G., Baxter, A., Tixeira, R, Jiang, L., Ozkocak, D., Santavanond, J., Hulett, M., Lock, P., Phan, T., Poon, I. “Defining the role of cytoskeletal components in the formation of apoptopodia and apoptotic bodies during apoptosis” Nature, 5 September 2019. https://link-springer-com.proxy.lib.odu.edu/content/pdf/10.1007/s10495-019-01565-5.pdf.
Sebbagh, M., Renvoize, C., Hamelin, J., Riche, N., Bertoglio, J., Breard, J. “Caspase-3-mediated cleavage of ROCK I induces MLC phosphorylation and apoptotic membrane blebbing” Nature, 6 March 2001. https://www.nature.com/articles/ncb0401_346.
Pucci, B., Kasten, M., Giordano, A. “Cell cycle and Apoptosis” National Library of Medicine, 4 July 2000. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1550296/#:~:text=Apoptosis%20is%20a%20highly%20conserved,undesirable%20inflammatory%20response%20%5B1%5D.