Response to the Signal

Free Response

What is a possible result of a mutation in a kinase that controls a pathway that stimulates cell growth?

Hint:

If a kinase is mutated so that it is always activated, it will continuously signal through the pathway and lead to uncontrolled growth and possibly cancer. If a kinase is mutated so that it cannot function, the cell will not respond to ligand binding.

How does the extracellular matrix control the growth of cells?

Hint:

Receptors on the cell surface must be in contact with the extracellular matrix in order to receive positive signals that allow the cell to live. If the receptors are not activated by binding, the cell will undergo apoptosis. This ensures that cells are in the correct place in the body and helps to prevent invasive cell growth as occurs in metastasis in cancer.

A scientist notices that a cancer cell line shows high levels of phosphorylated ERK in the absence of EGF. What are two possible explanations for the increase in phosphorylated ERK? Be specific in which proteins are involved.

Hint:

Possible explanations:

  1. EGFR dimer cannot separate.
  2. An upstream mutation (in Ras, Raf, MEK) constitutively activates the signaling cascade.
  3. ERK has a mutation that prevents it from binding to its phosphatase.
  4. The cell has a mutation preventing the expression or function of the ERK-specific phosphatase.