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Rabbit Kidney Cells with mEmerald-Actin and mApple-Paxillin

Phosphorylation (the addition of a phosphate group to a protein or other organic molecule) of paxillin in response to integrin-mediated cell adhesion and growth factor stimulation regulates interactions with many signaling and structural proteins including vinculin and Src. As a result, paxillin functions as a drafting scaffold for molecules into a signal transduction complex that is closely opposed to the plasma membrane.

The rabbit kidney epithelial cells (RK-13 line) featured in the digital video presented in this section were fluorescently labeled with mEmerald fused to actin and mApple fused to paxillin. Actin is a monomeric subunit of the microfilament, one of the basic components of the cytoskeleton. Actin was first observed via experimental means in the late 19th century, but the protein is usually considered to have been officially discovered more than 50 years later. Paxillin is a protein that concentrates at focal adhesions, which are important for cell motility. Research suggests that paxillin also functions as an adaptor protein involved in directing signal transmission downstream.

An enhanced variant of EGFP, mEmerald is bright and photostable. The peak excitation and emission wavelengths for mEmerald are 487 and 509 nanometers, respectively. mApple is a red fluorescent protein from the mFruit series of fluorescent proteins derived from mRFP1 using a directed evolution approach. mApple matures rapidly and is bright and photostable. Excitation and emission maxima of mApple occur at 568 and 592 nanometers, respectively.