Cell Communication and Signaling Pathways

Cell Communication

• Communication is essential between cells, between a cell and its environment (extracellular space), or between a cell and the extracellular matrix it resides on.
• These communications primarily occur through protein-protein interactions.

Long-Distance Signaling (Hormones)

• Long-distance signaling typically involves hormones.

Autocrine and Paracrine Signaling

• Both paracrine and autocrine signaling are mediated by secreted, soluble signals.
• These signals bind to receptors.
  • Autocrine: A cell signals to itself.
  • Paracrine: A cell signals to nearby cells.

Sequential Activation in Signaling Cascades

• Signaling often involves sequential activation of proteins.
• Example: A (activator) activates B (effector).
  • A is upstream of B and B is downstream of A.
  • Downstream and upstream refer to the positions within a signaling cascade related to a transcription factor.

Protein Conformation and Activation

• Protein activation involves a change in protein conformation.
• An activated protein activates another protein (e.g., A activates B).
• The activating protein can