Cell signalling

Introduction:

Cell signalling is the process of communication between cells through transmitting, receiving, and processing signals from the environment or neighbouring cells. Cell signalling plays a major role in maintaining the functions of our body. Cellular signalling starts its functioning from the early stage of development in the womb. It helps to maintain cooperation among the cells in all the stages of growth and development. In this blog, we will learn in detail about the stages of cell signalling, cell receptors, types of signalling, hormones in cell signalling, and cell signalling diseases.

Stages of Cell signalling:

Cell signalling can be categorised into three stages. They are 

1. Reception: It is the process of detection of signals by the cells. Cell receptors play a major role in the detection of signals.
2. Transduction: It is the process of transportation of signals from the external environment to the cell. It occurs in five sequential steps. They are:

• Reception
• Integration
• Amplification
• Target 
• Termination

1. Response: It is the cell’s feedback to a particular signal that strikes it.

Cell Receptors:

Cell receptors are found attached to the surface of the cell that facilitates cell signalling. It is made up of protein and can receive signals from the environment and neighbouring cells. Receptors are found attached to the plasma membrane, cytoplasm, or nucleus. The molecule which binds to the receptor during signalling is called a ligand. These cell receptors are classified into seven groups. They are:

1. G protein-coupled receptors
2. Receptor tyrosine kinases
3. Cytokine receptors
4. Wnt receptors
5. TGFβ receptors
6. Notch receptor
7. Hedgehog receptors

Types of signalling:

Based on the distance travelled by the signals, Signals are classified into three types. Those types of signalling are:

1. Autocrine signalling
2. Paracrine signalling
3. Endocrine signalling
4. Direct signalling

Autocrine signalling:

Autocrine signalling is the production of signals by a cell that can be detected by the same cell. It is communication that happens within the cell. Here, the cell that sends the signal and the target cell are the same. This type of signalling ensures the proper functioning of the cell. Autocrine signalling plays a major role in regulating pain sensation, apoptosis, viral infection response, and inflammatory feedback.

Paracrine signalling:

Paracrine signalling is sent to the cells nearby. These are short-time signals sent for immediate response. These signals are diffused through the extracellular matrix of cells. The most common molecule involved in this type of signalling is neurotransmitters. These signals help in maintaining cellular connections and coordination. Paracrine signalling plays a major role during the process of development.

Endocrine Signalling:

Endocrine signals travel long distances to reach the target cell. They are mostly initiated by endocrine cells and travel through the bloodstream. Hormones facilitate the transmission of the signal. This type of signalling is commonly found in the thyroid gland, pituitary gland, and hypothalamus. 

Direct signalling:

This is also called juxtacrine signalling. Direct signalling occurs through gap junctions. This is a simpler and quicker form of signal transmission. Gap junctions that lie between cell membranes transmit signals to the nearby cells by enhancing the movement of small molecules called intracellular mediators. This helps the cell send information quickly to its neighbouring cells. 

Hormones involved in Cell signalling:

Cell signalling to different organs of the body is facilitated by certain types of hormones specific to those organs. Some of the hormones involved in cellular signalling of some body parts are:

• Liver – Epinephrine and glucagon
• Adipose – Epinephrine, ACTH and 
• Glucagon
• Ovary – Luteinizing Hormone
• Skeletal Muscle – Epinephrine
• Kidney – Vasopressin (ADH)
• Cardiac Muscle – Epinephrine
• Vasopressin (ADH) – Thyroid Stimulating Hormone
• Bone – Parathyroid hormone
• Adrenal Cortex – Adrenocorticotropic Hormone (ACTH)

Cell signalling Diseases:

Defective cell signalling within the cell can result in various diseases. Some of the commonly caused diseases are Ageing, Alopecia, Alzheimer’s Disease, Asthma, Ataxia Telangiectasia (AT), Botulism, Cardiomyocyte Hypertrophy, Chronic Myelogenous Leukaemia (CML), Cockayne Syndrome, Cystic Fibrosis, Diabetes (Type 2 – Insulin Resistance), Glaucoma, Multiple Sclerosis, Parkinson’s Disease, Heart Disease, Neurofibromatosis, Norrie Disease, Pancreatic Cancer, Tuberous Sclerosis, Waardenburg Syndrome, and Werner Syndrome.

Importance of Cell signalling:

Cell signalling plays a major role in various functions of the body. They are:

• Cellular development
• Cell division
• Cellular migration
• Protein expression
• Apoptosis
• Immune response
• Cell differentiation
• Homeostasis balance

Conclusion:

Cell signalling controls a wide range of functions in our body. They direct the life cycle of every cell in the body, from cell division to apoptosis. Improper cell signalling can also result in myriads of diseases and disorders. In recent days, cell signalling research has been conducted to mitigate the growth of cancer cells. Cancer treatment is studied through cell signalling and receptors. Likewise, many types of research are performed to obtain solutions through cell signalling.