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Pig Kidney Cells with mEmerald-PMP and mApple-ER

The male pig kidney is the source of the LLC-PK1 cell line. The kidney functions primarily to divide toxins, urea, and other kinds of waste from the blood while still preserving the appropriate water, salt, and electrolyte levels. The nephron, which is composed of a renal corpuscle and tubule, is its fundamental filtering unit. In just one day, each human kidney filters around 160 quarts of material. Around 1 percent is excreted, and the rest of the material is reabsorbed by the nephrons.

Peroxisomes and the endoplasmic reticulum present in cultured LLC-PK1 cells were fluorescently tagged with mEmerald fused to a peroxisomal membrane protein (PMP) targeting signal and mApple fused to an ER targeting signal. Peroxisomes are membrane-bound microbodies first described by Christian de Duve, who was a co-recipient of the Nobel Prize for Physiology or Medicine in 1974 for his work with peroxisomes and lysosomes. A variety of enzymes are found inside peroxisomes, such as catalase and D-amino acid oxidase, that primarily function in ridding cells of hydrogen peroxide and other toxic substances. For many years, it was generally believed that peroxisomes were derived from the ER, but no convincing evidence for this view was ever found. Since the early 1980s, most researchers have held the view that peroxisomes form through their own division, but the debate regarding peroxisome synthesis is ongoing.

A member of the mFruit series of fluorescent proteins, mApple was developed via a directed evolution approach from mRFP1. Excitation of mApple peaks at 568 nanometers and emission peaks at 592 nanometers. The green fluorescent protein mEmerald is a variant of EGFP, an enhanced form of Aequorea GFP. Excitation and emission maxima of mEmerald occur at 487 and 509 nanometers, respectively.