Eukaryotic cells divide their metabolic labor between functionally distinct, membrane-enveloped organelles, each precisely tailored for a specific set of biochemical reactions. Peroxisomes are ubiquitous, endoplasmic reticulum-derived organelles that perform requisite biochemical functions intimately connected to lipid metabolism. Upon cell division, cells have to strictly control peroxisome division and inheritance to maintain an appropriate number of peroxisomes in each cell. Peroxisome division follows a specific sequence of events that include peroxisome elongation, membrane constriction, and peroxisome fission. Pex11 proteins mediate the elongation step of peroxisome division, whereas dynamin-related proteins execute the final fission. The mechanisms responsible for peroxisome membrane constriction are poorly understood. Molecular players involved in peroxisome inheritance are just beginning to be elucidated. Inp1p and Inp2p are two recently identified peroxisomal proteins that perform antagonistic functions in regulating peroxisome inheritance in budding yeast. Inp1p promotes the retention of peroxisomes in mother cells and buds by attaching peroxisomes to as-yet-unidentified cortical structures. Inp2p is implicated in the motility of peroxisomes by linking them to the Myo2p motor, which then propels their movement along actin cables. The functions of Inp1p and Inp2p are cell cycle regulated and coordinated to ensure a fair distribution of peroxisomes at cytokinesis.
"Peroxisomes are single-membrane organelles varying in size, shape, and biochemical content depending on cell type and environmental requirements –. The importance of peroxisomes for normal mammalian development has been shown by their linkage to many inherited diseases. "
[Show abstract][Hide abstract] ABSTRACT: In peroxisomes, peroxins (PEXs) 3 and 19 are the principal protein components of the machinery required for early peroxisomal biogenesis. For further insight into the interaction of PEX3 and PEX19, we used hydrogen exchange mass spectrometry to monitor conformational changes during complex formation between PEX3 and PEX19 in vitro. Our data showed that PEX19 remained highly flexible during interaction with PEX3. However, we could detect three changes, one each in the N-and C-terminus along with a small stretch in the middle of PEX19 (F64-L74) which became shielded from hydrogen exchange when interacting with PEX3. PEX3 became more protected from hydrogen exchange in the binding groove for PEX19 with only small changes elsewhere. Most likely the N-terminus of PEX19 initiates the binding to PEX3, and then subtle conformational changes in PEX3 affect the surface of the PEX3 molecule. PEX19 in turn, is stabilized by folding of a short helix and its C-terminal folding core permitting PEX19 to bind to PEX3 with higher affinity than just the N-terminal interaction allows. Thus within the cell, PEX3 is stabilized by PEX19 preventing PEX3 aggregation.
PLoS ONE 07/2014; 9(7):e103101. DOI:10.1371/journal.pone.0103101 · 3.23 Impact Factor
"During cell division, cells control the partition of organelles to the mother and daughter cell, to guarantee that both receive their required quota of organelles. Two proteins in yeast, termed inheritance of peroxisomes protein (Inp) 1 and 2, have important but opposite functions during organelle partition . Overexpression of Inp1 causes an increase in the number of daughter cells without peroxisomes, due to its function in "
[Show abstract][Hide abstract] ABSTRACT: Peroxisomes play a crucial role in regulating cellular metabolism, providing compartments where metabolic pathways can be contained and controlled. Their importance is underlined by the developmental brain disorders caused by peroxisome malfunction, while disturbances in peroxisome function also contribute to ageing. As peroxisomes do not contain DNA, they rely on an active transport system to obtain the full quota of proteins required for function. Organelle protein transport however, is rarely a one-way process and exciting recent data have demonstrated that peroxisomes can selectively export membrane and matrix proteins to fulfil specific functions. This review will summarize the current knowledge on peroxisomal membrane and matrix protein export, discussing the mechanisms underlying export as well as the role of peroxisomal protein export in peroxisomal and cellular function.
"It is believed that while de novo biogenesis of peroxisomes can occur directly from the ER, existing peroxisomes in a cell can also undergo fission to form more peroxisomes (Motley and Hettema, 2007). These recent molecular genetic and biochemical evidence have been taken into account in recent reviews (Tabak et al., 2003, 2013; Titorenko and Mullen, 2006; Fagarasanu et al., 2007) and resulted in models such as the “ER semi-autonomous peroxisome maturation and replication” for peroxisome biogenesis in plants (Mullen and Trelease, 2006; Trelease and Lingard, 2006) and for yeasts (Titorenko and Rachubinski, 2009). Additional detailed discussion on peroxisome biogenesis can be found in recent reviews by Hu et al. (2012), Tabak et al. (2013), and Theodoulou et al. (2013). "
[Show abstract][Hide abstract] ABSTRACT: Transmission electron micrographs of peroxisomes in diverse organisms, including plants, suggest their close association and even luminal connectivity with the endoplasmic reticulum (ER). After several decades of debate de novo peroxisome biogenesis from the ER is strongly favored in yeasts and mammals. Unfortunately many of the proteins whose transit through the ER constitutes a major evidence for peroxisome biogenesis from the ER do not exhibit a similar localization in plants. Consequently, at best the ER acts as a membrane source for peroxisome in plants. However, in addition to their de novo biogenesis from the ER an increase in peroxisome numbers also occurs through fission of existing peroxisomes. In recent years live-imaging has been used to visualize peroxisomes and the ER but the precise spatio-temporal relationship between the two organelles has not been well-explored. Here we present our assessment of the peroxisome-ER relationship through imaging of living Arabidopsis thaliana plants simultaneously expressing different color combinations of fluorescent proteins targeted to both organelles. Our observations on double transgenic wild type and a drp3a/apm1 mutant Arabidopsis plants suggest strong correlations between the dynamic behavior of peroxisomes and the neighboring ER. Although peroxisomes and ER are closely aligned there appears to be no luminal continuity between the two. Similarly, differentially colored elongated peroxisomes of a drp3a mutant expressing a photoconvertible peroxisomal matrix protein are unable to fuse and share luminal protein despite considerable intermingling. Substantiation of our observations is suggested through 3D iso-surface rendering of image stacks, which shows closed ended peroxisomes enmeshed among ER tubules possibly through membrane contact sites (MCS). Our observations support the idea that increase in peroxisome numbers in a plant cell occurs mainly through the fission of existing peroxisomes in an ER aided manner.
Frontiers in Physiology 07/2013; 4:196. DOI:10.3389/fphys.2013.00196 · 3.53 Impact Factor
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