Exam 4- Cell Signaling Notes

Cell Signaling

Signaling Molecules

• Bind to specific receptors.
  • Some receptors can bind multiple signals; specificity is still important.
• Hydrophobic signaling molecules:
  • Utilize intracellular receptors.
• Hydrophilic signaling molecules:
  • Utilize cell surface receptors.
• Distance:
  • Long distance: Endocrine signaling.
  • Short distance: Paracrine, autocrine, and juxtacrine signaling.

Mode of Cell Signaling

1) Direct Cell-to-Cell Contact:

• Direct interaction between cells.
• Factors involved include integrins and cadherins.
• Example:
  • Juxtacrine signaling requires cells to be right next to or in direct contact with each other.

2) Secreted Molecules (Distance):

• Endocrine:
  • Long distance signaling.
  • Signal molecules are carried through the circulatory system.
  • Examples: Estrogen, pituitary, and thyroid hormones.
• Paracrine:
  • Short distance signaling.
  • Sends signals to nearby cells.
  • Neuronal signaling is a mix of both paracrine and endocrine signaling.
  • Examples: Dopamine, Histamine.
• Juxtacrine:
  • Very short distance signaling.
  • Cells are essentially right next to each other.

Steroid Hormones

• Hydrophobic signaling molecules.
• Utilize intracellular receptors.
• Examples:
  • Testosterone, estrogen, and corticosteroids (glucocorticoids, mineralocorticoids).
  • Ecdysone: The driving steroid hormone in insects that causes ecdysis (shedding of the outer layer).
  • Brassinosteroids: Plant hormones.

Nitric Oxide

• Important paracrine signaling molecule.
• Induces relaxation.

Neurotransmitters

• Utilized by dopamine.
• Travel across synapses in synaptic vesicles.

Peptide Hormones

• Animal Peptides: Insulin
• Nucelopeptides: Endorphins
• Polypeptides: NGF, EGF, PDF
  • NGF: Nerve Growth Factor
  • EGF: Epidermal Growth Factor
  • PDGF: Platelet-Derived Growth Factor

Plant Hormones

• Auxins: Plant development
• Gibberellins: Stem elongation
• Ethylene: Fruit ripening
• Cytokinins: Cytokinesis