In this section learn that many signaling pathways ultimately pass messages to the nucleus of a cell.

Many signaling pathways ultimately pass messages to the nucleus of a cell. The Raf protein (shown in white) activates another messenger protein (in brown) as it passes through fibers that make up the cell's cytoskeleton. The signal is passed to yet another messenger (in purple). These messenger proteins are known as kinases, enzymes with the ability to activate other proteins through the addition of phosphate groups. This protein travels to the nucleus past cellular organelles such as the mitochondria (in glowing orange) and the network of membranes known as the endoplasmic reticulum (shown in light brown). Molecules identified: Raf: A protein that interacts with the Ras protein. Raf is an example of a kinase enzyme, able to activate other proteins by adding phosphate molecules to serine and threonine amino acids. Mutations in the Raf protein are present in a large percentage of human malignant melanomas. Mitogen-activated protein (MAP) kinases: These enzymes – sometimes known as extracellular signal-regulated kinases (ERKs) – add phosphates to other proteins to activate or deactivate them. Mutations in these kinases can disrupt cell signaling and cause abnormal cell growth and proliferation. These proteins are good targets for drugs against cancer.

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