Molecular Paddling of White Blood Cells

Shrestha Sherry Chakraborty, Amity University Kolkata.

Cells have employed various ways to travel in the biological system.  Somatic cells in our body adhere to cell surfaces for their movement. On the other hand, sperm cells and some bacteria move by the means of flagella. White blood cells are the specialized cells of the immune system. They are broadly classified into five major categories namely: Basophil, Neutrophil,  Eosinophil, Monocytes, and Lymphocytes respectively. 

Being a part of the immune system, they perform a wide array of important functions like initiating an inflammatory response by releasing histamines or by initiating phagocytosis of harmful pathogens. Infections can occur anywhere in the biological system. Thus, how these white blood cells move throughout the body is of immense importance. 

White blood cells or leukocytes are known to move around in our bodies. Their movement has been studied and observed by scientists for years mainly to gain insight on how not only white blood cells but also malignant cells move from one place to another in the body causing cancer metastasis. The movement of white blood cells is especially of utmost importance. Their migration is especially important during diseases like cancer. It is mainly known that leukocytes cannot migrate from one place to another without being attached to the cellular surfaces or without prior support. 

Studies conducted previously have shown leukocytes to swim but no mechanism by which these cells migrate throughout the body was identified. However, it is now widely accepted that cells moving without flagellum require the cell shape to be altered. However, recent studies conducted show that the leukocytes can swim in two-dimensional surfaces without adhering to them and as well as without altering their shape. 

Looking at the leukocytes, it gives an illusion as if they move their body like a swimmer. The leukocytes move using transmembrane proteins that extend out from their cellular membranes. Rearward movement of the cell surface of leucocytes helps them to move in a solid and liquid medium which can be with or without adhesion. Considering the cell membrane of the cell, it does not move by the above-mentioned process. Some transmembrane proteins are associated with the cytoskeletal framework of the cell as well. When they contract, the cells move forward.

The leukocytes use molecular paddling that is, actin driven external treadmilling and recycling of actin-associated transmembrane proteins through vesicular transport. Cell membrane recycling was being studied by scientists for a long period but its function in the movement of a cell from one location to another was never considered. The authors stated that this type of movement of immune cells may help them to migrate to inflamed, fluid-filled, and infected parts of the body. 

Moreover, the scientists wish to investigate the function of molecular paddling in other circumstances in the biological systems and also if cells other than leukocytes use this specialized mechanism of molecular paddling for transportation. 

Also read: COVID-19: Vaccine Development Probe

Source: 

1. Laurene Aoun, Alexander Farutin, Nicolas Garcia-Seyda, et al.; Amoeboid Swimming Is Propelled by Molecular Paddling in Lymphocytes; 2020; Biophysical Journal; Vol: 119 (6), P1157-1177; DOI: http://10.1016/j.bpj.2020.07.033

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