INTERCELLULAR COMMUNICATION AND SIGNAL TRANSDUCTION . DR. ZAHOOR ALI SHAIKH LECTURE--- 4 . INTERCELLULAR COMMUNICATION. HOW CELLS COMMUNICATE WITH ONE ANOTHER ? Intercellular communication can take place either directly or indirectly .
DR. ZAHOOR ALI SHAIKH
It involves physical contact between the cells.
i) Through Gap Junctions
ii) Through Surface Markers
In some tissues minute tunnel or gap are present between the neighboring cells. Through gap junctions, small ions and molecules are exchanged between the cells, without ever entering the extracellular fluid. Gap junctions are present in cardiac muscle.
Some cells like those of immune system, have specialized markers on the surface of membrane that can recognize body own cells and selectively destroy only undesirable cells e.g. cancer cells.
Release of Histamine by connective tissue cell during tissue injury. Histamine causes local vasodilatation to increase blood flow.
Nerve communicate with the cells, they innervate by releasing Neurotransmitters. Neurotransmitter diffuses through narrow extracellular space (cleft) to act locally on target i.e. another neuron, muscle, or gland.
Hormone are long range chemicals messengers, secreted into blood by Endocrine glands. They effect on target cells, some distance away from their site of release.
1. By opening or closing chemically gated receptor channels e.g. Na+, K+
2. By activating receptor – enzyme e.g. protein kinases
3. By activating second messenger via G-Protein
[a]. When first messenger, which is chemical messenger brings signal to the receptor.
[b]. Binding of first messenger to the receptor activates G-Protein.
[c]. G-Protein acts via second messenger
- Cyclic Adenosine Mono Phosphate [cAMP]
- or It may be Ca2+.
And causes required bio-chemical reactions in the cell
G-Protein activates Adenylyl Cyclase enzyme.
1. Cyclic AMP [cAMP]
- Direct – through gap junction
- through surface markers
- Indirect – paracrine,
- By opening or closing chemically gated receptor channel
- By activating receptor enzymes
- By activating second messenger by G protein coupled receptors