Introduction
Cells digest substances for energy production. The material is taken inside the cell through a process known as endocytosis. The material taken inside the capsulated structure is called endocytotic vacuoles. The lysosomes help in the digestion of these materials. The acid hydrolases present inside these lysosomes digest the molecules inside the vacuoles.
Why Is Heterophagy Important in the Normal Physiology of the Body?
By the process of digestion in heterophagy, the toxins are removed from the body. The dead or damaged cells are also phagocytized in this manner. Therefore they help in the elimination of waste products and toxins from infection and clear the space of dead remains by engulfing them. Most mammalian beings exhibit heterophagy. Heterophagy can follow different pathways of the destruction of cells outside the organelle or from within. For example, in intestinal amoebic parasites like entamoeba histolytica large number of parasites are engulfed. Such invasion is seen directly pooled in the intestines. Whereas the intracellular parasites exhibit heterophagy inside the infected host cells. For example, in plasmodium falciparum parasite, ingestion of proteins and hemoglobin is done within the cell by endocytosis. This is helpful in understanding the pathway and development of drugs. Certain apicomplexan parasites use heterophagy for the replication of host cells like plasmodium and toxoplasma. The nutrients present in the host cells are much required for the phagocytic activity to take place.
How Is the Function of Heterophagy Carried Out?
It is the lysosomes that help in carrying out the digestion process in heterophagy. These lysosomes contain a phospho-bilipid layer. One side of this layer is hydrophobic (avoiding water) and the other surface is hydrophilic (loves water). The phospholipid present in these layers carries out the process of digestion, elimination, and decomposition of toxins. Both micromolecules like ions (sodium and potassium) and macromolecules like proteins and nucleic acids are phagocytized by these lysomatic acids and enzymes. The binding of certain bacteria like E. histolytica increases virulence in pathogenic strains. Thus E. histolytica can use heterophagy as a sensory pathway to regulate the virulence factors and detect its environmental resources. This can increase its ability to cause disease. Heterophagy also contributes to the evasion of host immunity. It paves pathways for parasitic survival and pathogenesis.
What Are the Main Functions of Heterophagy?
The lysosomes, which are responsible for heterophagic activity in a cell, are produced by the energy storehouse of the body known as the golgi apparatus. Lysosomes are membrane bound organelles. These organelles are not only limited to self-destructive function but also have other functions like:
-
Recycling of old cells.
-
Digestion of materials both on the inside and outside.
-
Production of enzymes.
-
Decomposition of toxins.
-
Elimination of toxins.
-
Protein synthesis.
-
Breaking down dead cells.
-
Breaking down macromolecules.
-
Helps in exocytosis.
What Is an Endocytic, Pinocytic, and Phagocytic Process?
Processes like phagocytosis, endocytosis, and pinocytosis are cell-mediated mechanisms for the elimination or destruction of toxins by digesting them.
Endocytosis: As the name suggests, endo means inside, and cytosis means destruction, so it is the destruction of a substance from within the cell. The engulfation process is carried out in a pocket-like structure called a vesicle. This vesicle further fuses with the lysosome. Over there, the substance is broken down for the usage of cells. Endocytosis is further classified into pinocytosis and phagocytosis.
Pinocytosis: Pinocytosis is the engulfing of substances derived from a fluid. It also shows an interesting feature of developing pinocytotic bubbles. These are formed at the outer wall of the plasma membrane. They are short and slender and surround the fluid. These bubbles invaginate within the cell also. This bubble-like structure helps in the free transportation process across the intracellular area. Pinocytosis is observed in amoeba, endothelium of blood vessels, and epithelial cells of renal and intestinal tubules. The act of pinocyte is initiated by gamma globulin, gelatin, and certain salts. This mechanism allows the passage of high molecular weight compounds into the cells, like protein and carbohydrates.
Phagocytosis: Phagocytosis is the engulfation of toxins that are visible under the microscope. The phagocytic activity led by a chemical is known as chemotaxis. Phagocytic action is followed by antibody generation. In some bacterial infections, phagocytosis takes place only when its specific antibody is released. It is an effective mechanism against any infections. Protozoa obtain their food through phagocytosis. The invasion of foreign substances in the body is discarded in this manner. However, in some conditions, diseases caused by bacteria like tuberculosis and brucellosis can survive inside the body of its descendant phagocytes for years which ingested them. Phagocytosis can be within the cell or outside. White blood cells show phagocytic activity and play an important role in the body’s immune system.
How Does the Lysosomal Malfunction Affect the Body?
Lysosomes are an integral part of a well-maintained cell. Any damage to it can cause disruption in the physiology of cells. Such as the buildup of sugar and lipids in the body. Lysosomal storage diseases are caused by defective genes. Children can possess it from a single parent or both defective genes. This condition can be life-threatening. Lysosomal storage disease can kill the cells and cause pathophysiology in other organs like the liver, spleen, and brain. This can turn out to be fatal. Some of the lysosomal storage diseases are Krabbe disease, metachromatic leukodystrophy, and Tay-Sachs disease.
Hence the absence of lysosomes can affect the normal activities of the body, like the synthesis of proteins. Some of which are crucial in the egg fertilization process as well. Accumulation of toxins can lead to other serious conditions.
Conclusion
The toxins broken down through heterophagy can be biosynthesized through the recycling process. New organelles can be made like this, or autolysis is initiated. The protein synthesis caused by heterophagy is useful in cell-to-cell interactions. Lysosomal activity has proven beneficial in the bone regenerative processes and other metabolic activities of the body.
