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Cell to Cell Communication Cell Signaling results in a change in cell activity Cell to Cell Communication • Examples: • neurotransmitters recognized in synapse or neuromuscular junction • Antigens triggering antibody response • Target cells responding to specific hormones Cell to Cell Communication • Often involves specialized receptors called integrins • Integins are transmembrane proteins that provide a link between the interior and exterior of the cell Cell to Cell Communication • Involved in specific processes such as differentiation, migration, proliferation, protein expression, activation of growth factors, apoptosis, and cell survival. Can also be activated from the inside to change the cell’s relationship with its environment Kinases, a group of enzymes that control the cell cycle are activated by integrins Cell to Cell Communication • Integrins are heterodimers • Two different protein strands together • Alpha and beta chains • 24 integrins have been identified Integrins • Basic heterodimer structure has been highly conserved among all animals • What does this mean? • Similar proteins are also found in plants, fungi, and prokaryotes Integrin Activation Integrin Activation • Inactive: bent • Activated: Upright • This change occurs when a protein binds to a small section of the beta subunit. • What attaches to the integrin is called the ligand—could be a hormone, an antigen, etc. After activation… • Integrins move within the cell membrane to cluster and form adhesion sites • These sites bind with other proteins and serve as a link to the cytoskeleton • Sets off a cascade of events Integrin Activation • May be be outside-in OR • Inside out signaling Cell Signaling causes a change in cellular activity! • There will be a result! Could be initiation of cell cycle, formation of a blood clot, activation of a gene to produce a protein, etc.