Probing Peroxisome Dynamics and Biogenesis by Fluorescence Imaging

Abstract

Peroxisomes are the most recently discovered classical organelles, and only lately have their diverse functions been truly recognized. Peroxisomes are highly dynamic structures, changing both morphologically and in number in response to both extracellular and intracellular signals. This metabolic organelle came to prominence due to the many genetic disorders caused by defects in its biogenesis or enzymatic functions. There is now growing evidence that suggests peroxisomes are involved in lipid biosynthesis, innate immunity, redox homeostasis, and metabolite scavenging, among other functions. Therefore, it is important to have available suitable methods and techniques to visualize and quantify peroxisomes in response to various cellular signals. This unit includes a number of protocols that will enable researchers to image, qualify, and quantify peroxisome numbers and morphology-with both steady-state and time-lapse imaging using mammalian cells. The use of photoactivatable fluorescent proteins to detect and measure peroxisome biogenesis is also described. Altogether, the protocols described here will facilitate understanding of the dynamic changes that peroxisomes undergo in response to various cellular signals. Curr. Protoc. Cell Biol.

Peroxisome Plasticity at the Virus–Host Interface

“…Due to the fundamental nature of peroxisomes as multifunctional and dynamic organelles, the aspects of peroxisome biology required for virus infections will be broadly applicable to human health and disease. This is already apparent in the themes present across biological conditions, as discussed above: changes to peroxisome biogenesis are found in metabolic disorders [27,30], development [2,4,6], cancer [9], and stress responses [23], while enhanced peroxisome-mediated ROS processing occurs in tumors [68] and plant infections [29,55], and peroxisomal immune signaling has been implicated in a variety of processes [3,9,31], among others. Additionally, in a strikingly similar vein to virus infections, the gut microbiota is known to widely regulate PPARs in a tissue-specific manner [69], and pathological microbial infections require peroxisome metabolism, both of ROS and lipids [70].…”

“…Numerous studies have linked peroxisome dynamics to condition- or organism-specific peroxisome functions. For example, PEX genes are upregulated [23] and peroxisomes are elongated [8,24,25] during cell stress, and peroxisome numbers are increased in cell types with elevated lipid catabolism [26,27], during mitosis [6], in cancerous cells [9], and during cell differentiation [4,28]. These changes may enhance metabolic output for the high energy consumption required for these processes.…”

“…This discovery prompted much effort towards characterizing the peroxisomemediated immune response [2,3], redefining the scientific community's view of peroxisomes as major cellular organelles. In fact, peroxisomes are multifunctional and dynamic, and are known to play a variety of critical roles in development [4][5][6], cellular stress [7,8], cancer [9], and virus infection in plants [10]. Despite this, and the knowledge that human viruses cause extensive changes in other host organelles [11], peroxisomal characteristics beyond immune signaling have not been deeply investigated in cells under invasion by pathogens.…”