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Peroxisomes are remarkably plastic and dynamic organelles, which fulfil important functions in hydrogen peroxide and lipid metabolism rendering them essential for human health and development. Despite great advances in the identification and characterization of essential components and molecular mechanisms associated with the biogenesis and function of peroxisomes, our understanding of how peroxisomes are incorporated into metabolic pathways and cellular communication networks is just beginning to emerge. Here we address the interaction of peroxisomes with other subcellular compartments including the relationship with the endoplasmic reticulum, the peroxisome-mitochondria connection and the association with lipid droplets. We highlight metabolic cooperations and potential cross-talk and summarize recent findings on peroxisome-peroxisome interactions and the interaction of peroxisomes with microtubules in mammalian cells.

Pex11 proteins are involved in membrane remodelling processes of peroxisomes, and are key components of peroxisomal division and proliferation. In mammals, three Pex11 isoforms, Pex11α, Pex11β, and Pex11γ exist. Here we demonstrate that Pex11β, but not Pex11α or Pex11γ, is almost exclusively extracted from peroxisomal membranes of paraformaldehyde-fixed cells by permeabilisation with the non-ionic detergent Triton X-100. This results in diminished detection of Myc-Pex11β in immunofluorescence preparations and appearance of the protein in the Triton X-100 extract. To our knowledge, Pex11β is the first peroxisomal membrane protein showing such a peculiar behaviour. Loss of Pex11β can be avoided by permeabilisation with digitonin, the addition of glutaraldehyde to the fixative, or the expression of a Pex11 fusion protein with a larger protein tag (e.g. YFP). Our observations further point to different functions and biochemical properties of the Pex11 isoforms within the peroxisomal membrane and during peroxisome proliferation.

Peroxisomes contribute to several crucial metabolic processes such as β-oxidation of fatty acids, biosynthesis of ether phospholipids and metabolism of reactive oxygen species, which render them indispensable to human health and development. Peroxisomes are highly dynamic organelles that rapidly assemble, multiply and degrade in response to metabolic needs. In recent years, the interest in peroxisomes and their physiological functions has significantly increased. This review intends to highlight recent discoveries and trends in peroxisome research, and represents an update as well as a continuation of a former review article. Novel exciting findings on the biological functions, biogenesis, formation and degradation of peroxisomes, on peroxisomal dynamics and division, as well as on the interaction and cross-talk of peroxisomes with other subcellular compartments are addressed. Furthermore, recent findings on the role of peroxisomes in the brain are discussed.