by JIGAR S. MEHTA Asst. Professor ( BIOCHEMISTRY ) M.Sc. B.Ed. M.B.A. ADVANCE STUDIES IN CELL BIOLOGY ----------------------Cell-Cell Interactions--------------- by JIGAR S. MEHTA Asst. Professor ( BIOCHEMISTRY ) M.Sc. B.Ed. M.B.A.

OVERVIEW OF THE UNIT 5.1 CYTOSKELETON 5.2 Cell movements & locomotion 5.3 CELL CELL INTERACTION 5.4 OVERVIEW OF STEM CELLS (SC) 5.5 Cancer Biology -Microfilaments - signal Cancer -Microtubules Amoeboid -Intermediate Filaments - types of signal -Potency Types Cyclosis -Types of stem cells: Tumors & their types Flagellated - pathway Ciliated - mechanism BSC Causes MSC Molecular transport - receptor Molecular basis - types of receptor OSC TSC Prevention & 3 Therapies i) Intracellular PSC ii) Cell surface receptor USC ESC a) G protein linked ASC -Stem Cells b) Enzyme linked Therapy c) Ion channel linked

5.1 Cell Cell Interactions Cell–cell interaction refers to the direct interactions between cell surfaces that play a crucial role in the development and function of multicellular organisms. These interactions allow cells to communicate with each other in response to changes in their microenvironment. This ability to send and receive signals is essential to the survival of the cell. Interactions between cells can be stable such as those made through cell junctions. These junctions are involved in the communication and organization of cells within a particular tissue.  Cells may receive a variety of signals, chemical signals, electromagnetic signals, and mechanical signals.  Types of cell signaling: Cells communicate through any of four basic mechanisms, depending primarily on the distance between the signaling and responding cells

Direct Contact: cells in direct contact with each other may send signals across gap junctions. Paracrine Signaling: secretions from one cell have an effect only on cells in the immediate area. Endocrine Signaling: signals are released into the circulatory system, which carries them to the target cells. Synaptic Signaling: In animals, the cells of the nervous system provide rapid communication with distant cells. Their signal molecules, neurotransmitters, do not travel to the distant cells through the circulatory system like hormones do. Rather, long, fiberlike extensions of nerve cells release neurotransmitters from their tips very close to the target cells. The narrow gap between the two cells is called a chemical synapse.

SIGNAL-TRANSDUCTION PATHWAY The process by which a signal on a cell’s surface is converted into a specific cellular response In reception, a chemical signal binds to a cellular protein, typically at the cell’s surface. In transduction, binding leads to a change in the receptor that triggers a series of changes along a signal-transduction pathway. In response, the transduced signal triggers a specific cellular activity.

SIGNALLING MECHANISMS: Signalling procedure differs based on where their receptors are located & receptors are of mainly two type: intra cellular and cell surface receptor. Many cell signals are lipid-soluble or very small molecules that can readily pass across the plasma membrane of the target cell and into the cell, where they interact with a receptor. Some bind to protein receptors located in the cytoplasm; others pass across the nuclear membrane as well and bind to receptors within the nucleus. These intracellular receptos may trigger a variety of responses in the cell, depending on receptor.

G - PROTEIN LINKED RECEPTORS A widespread system for signal transduction & Produce second messengers to elicit a cell response. The G protein acts as an on-off switch. If GDP is bound, the G protein is inactive. If GTP is bound, the G protein is active.  G-PROTEIN is trimeric protein and receptor is made up of 7 transmembrane polypeptide chains. When signal bind to receptor, GDP is replaced by GTP, and G-protein will become active. And alfa sub-unit liberate from that and move towards enzyme(adnylyl cyclase) which also become active and it adnylyl cyclase convert ATP to cAMP, and then start enzymatic reaction & then will give cellular response.