Intracellular Receptors and Transcription Regulation

Introduction

• Many cell signals are small, lipid-soluble molecules.
• These molecules can readily cross the cell membrane.
• They interact with receptor proteins in the cytoplasm or nucleus.

Function of Intracellular Receptors

• Intracellular receptors can trigger a variety of cellular responses.
• Some receptors act specifically as regulators of gene transcription.

Mechanism of Transcription Regulation

• Binding Site for DNA:
  • Receptors have a DNA binding site.
  • Inactive state: DNA binding site is occupied by an inhibitor protein.
• Activation Process:
  • A signal molecule binds to another site on the receptor.
  • The inhibitor is released, exposing the DNA binding site.
• Receptor Activation:
  • The receptor enters the nucleus.
  • It binds to a specific nucleotide sequence on the DNA.
  • This binding activates transcription of a particular gene.
  • The gene is usually located adjacent to the regulatory site.

Target Cell Response

• The response of the target cell depends on the nature of the cell.
• Different cells may have different reactions to the same signal molecule.