Biology subjects

Simmonds, A. J.

Publications and source records attributed to Simmonds, A. J..

3 recordsLinked to original sources

bioRxiv2019

Drosophila melanogaster Peroxisome Biogenesis Factor 7 plays a role in embryonic development

Peroxisomes are organelles responsible for aspects of lipid metabolism and management of reactive oxygen species. Peroxisome Biogenesis Factor (Peroxin, Pex) genes encode proteins essential to peroxisome biogenesis or function. In yeast and mammals, PEROXIN7 acts as a cytosolic receptor protein that targets a subset of enzymes for peroxisome matrix import.\n\nProteins targeted by PEROXIN7 contain a peroxisome targeting sequence 2 (PTS2) motif. The PTS2 was not found in the D. melanogaster homologs of proteins that are PEROXIN7 targets in yeast or mammals, however comparative genomics suggest a Pex7 homolog is present in the D. melanogaster genome. Herein we report novel, tissue-specific patterns for transcription and translation of Pex7 in the D. melanogaster embryo that appear to be strongest in presumptive neuronal lineages. We also show that targeted somatic Pex7 knockout in neural precursors via targeted somatic CRISPR knockout affected survival of mutant embryos. Pex7 over-expression via Gal4-UAS also reduced adult survival but was not deleterious at the embryo stage. Notably, targeted somatic rescue of Pex7 in the neural precursors of Pex7 homozygous mutants also impaired embryo survival. We conclude that D. melanogaster has tissue-specific developmental requirements of Pex7 expression. This may be related to the requirement for peroxisome-mediated lipid synthesis in cells of the central nervous system.

genetics↗

bioRxiv2019

Impaired peroxisomal import in Drosophila hepatocyte-like cells induces cardiac dysfunction through the pro-inflammatory cytokine Upd3

Age is a major risk factor for cardiovascular diseases. Currently, the non-autonomous regulation of age-related cardiac dysfunction is poorly understood. In the present study, we discover that age-dependent induction of cytokine unpaired 3 (Upd3) in Drosophila oenocytes (hepatocyte-like cells), due to a dampened peroxisomal import function, is the primary non-autonomous mechanism for elevated arrhythmicity in old hearts. We show that Upd3 is significantly up-regulated (52-fold) in aged oenocytes. Oenocyte-specific knockdown of Upd3 is sufficient to block aging-induced cardiac arrhythmia. We further show that the age-dependent induction of Upd3 is triggered by impaired peroxisomal import and elevated JNK signaling in aged oenocytes. Intriguingly, oenocyte-specific over-expression of Pex5, the key peroxisomal import receptor, restores peroxisomal import, blocks age-related Upd3 induction, and alleviates aging- and paraquat-induced cardiac arrhythmicity. Thus, our studies identify an important role of the evolutionarily conserved pro-inflammatory cytokine signaling and hepatocyte-specific peroxisomal import in mediating non-autonomous regulation of cardiac aging.

physiology↗

bioRxiv2018

Functional characterization of peroxisome biogenic proteins Pex5 and Pex7 of Drosophila

Peroxisomes are ubiquitous membrane-enclosed organelles involved in lipid processing and reactive oxygen detoxification. Mutations in human peroxisome biogenesis genes (Peroxin, PEX) cause progressive developmental disabilities and, in severe cases, early death. PEX5 and PEX7 are receptors that recognize different peroxisomal targeting signals called PTS1 and PTS2, respectively, and traffic proteins to the peroxisomal matrix. We characterized mutants of Drosophila melanogaster Pex5 and Pex7 and found that adult animals are affected in lipid processing. Moreover, Pex5 mutants exhibited severe developmental defects in the embryonic nervous system and muscle, similar to what is observed in humans with Pex5 mutations, while Pex7 fly mutants were weakly affected in brain development, suggesting different roles for Pex7 in fly and human. Of note, although no PTS2-containing protein has been identified in Drosophila, Pex7 from Drosophila can function as a bona fide PTS2 receptor because it can rescue targeting of the PTS2-containing protein Thiolase to peroxisomes in PEX7 mutant human fibroblasts.

cell biology↗