Module 5 Notes

Introduction

• Focus on cellular processes related to cell number:
  • Growth and proliferation of cells
  • Apoptosis (programmed cell death)
• Balance between proliferation and apoptosis is crucial in normal tissue.
• Imbalance can lead to cancer:
  • Fewer cells die or more cells proliferate.

Mitogen-Activated Tyrosine Kinase Receptor

• Also known as receptor tyrosine kinases (RTKs).
• Function as cell surface receptors transmitting signals from outside to inside the cell.
• Relays messages by phosphorylating tyrosine, an amino acid.
• Activated by mitogens, which signal mitosis and cell division.

Cell Signaling Overview

• Cells communicate with the outside via receptors on the cell surface.
• Signal Reception:
  • Mitogens bind to receptors, triggering a response.
• Relay Process:
  • Message is transmitted from cell membrane to inside the cell.
• Integration and Amplification:
  • Signal integration involves multiple pathways.
  • Amplification ensures a big response from a single signal.
• Response:
  • Could involve metabolic enzymes, cytoskeleton changes, or gene transcription.

Mechanism of Receptor Tyrosine Kinase

• RTKs form dimers and float in cell membranes.
• Activation requires dimerization and cross-linking by a signal.
• Intracellular kinase domains come into contact, triggering phosphorylation.
• Phosphorylation:
  • ATP is used to add phosphates to proteins, altering their activity.
  • Phosphates are bulky and negatively charged, affecting protein shape and function.

Kinase Activity

• Kinases are enzymes that add phosphate groups to proteins.
• Auto-phosphorylation:
  • RTKs phosphorylate themselves (auto-phosphorylation).
  • This creates docking sites for proteins, advancing the signaling cascade.

Protein Interaction Mechanisms

• Covalent Modification:
  • Involves adding groups like phosphates, methyles, ubiquitin, or severing parts of proteins.
• Touch Interaction:
  • Proteins interact by changing each other's conformations through physical contact.

Key Takeaways

• Cell number regulation is vital for preventing cancer.
• RTKs play a critical role in signaling pathways, influencing cell growth and division.
• Understanding kinase activity and protein interactions is crucial for grasping cell signaling mechanisms.