Organisms produce high levels of reactive oxygen species (ROS) to kill pathogens or act as signaling molecules to induce immune responses; however, excessive ROS can result in cell death. To maintain ROS balance and cell survival, mitophagy selectively eliminates damaged mitochondria via mitophagy receptors in vertebrates. In marine invertebrates, however, mitophagy and its functions remain largely unknown. In the current study,
Vibrio splendidus
infection damaged mitochondrial morphology in coelomocytes and reduced mitochondrial membrane potential (ΔΨm) and mitophagosome formation. The colocalization of mitochondria and lysosomes further confirmed that lipopolysaccharide (LPS) treatment increased mitophagy flux. To explore the regulatory mechanism of mitophagy, we cloned Bcl2/adenovirus E1B 19 kDa protein-interacting protein 3 (BNIP3), a common mitophagy receptor, from sea cucumber
Apostichopus japonicus
(
AjBNIP3
) and confirmed that AjBNIP3 was significantly induced and accumulated in mitochondria after
V. splendidus
infection and LPS exposure. At the mitochondrial membrane, AjBNIP3 interacts with microtubule-associated protein 1 light chain 3 (LC3) on phagophore membranes to mediate mitophagy. After
AjBNIP3
interference, mitophagy flux decreased significantly. Furthermore, AjBNIP3-mediated mitophagy was activated by ROS following the addition of exogenous hydrogen peroxide (H
2
O
2
), ROS scavengers, and ROS inhibitors. Finally, inhibition of BNIP3-mediated mitophagy by
AjBNIP3
small interfering RNA (siRNA) or high concentrations of lactate increased apoptosis and decreased coelomocyte survival. These findings highlight the essential role of
AjBNIP3
in damaged mitochondrial degradation during mitophagy. This mitophagy activity is required for coelomocyte survival in
A. japonicus
against
V. splendidus
infection.
Reported herein is the hydride transfer initiated redox-neutral cascade cyclizations of aurones, providing a variety of [6,5] spiro-heterocycles in satisfactory yields and good diastereoselectivities.
Neuropeptides are released by neurons that are involved in a wide range of brain functions, such as food intake, metabolism, reproduction, and learning and memory. A full-length cDNA sequence of an FMRFamide gene isolated from the cuttlefish Sepia pharaonis (designated as SpFMRFamide) was cloned. The predicted precursor protein contains one putative signal peptide and four FMRFamide-related peptides. Multiple amino acid and nucleotide sequence alignments showed that it shares 97% similarity with the precursor FMRFamides of Sepiella japonica and Sepia officinalis and shares 93% and 92% similarity with the SpFMRFamide gene of the two cuttlefish species, respectively. Moreover, the phylogenetic analysis also suggested that SpFMRFamide and FMRFamides from S. japonica and S. officinalis belong to the same sub-branch. Tissue expression analysis confirmed that SpFMRFamide was widely distributed among tissues and predominantly expressed in the brain at the three development stages. The combined effects of SpFMRFamide+SpGnRH and SpFLRFamide+SpGnRH showed a marked decrease in the level of the total proteins released in the CHO-K1 cells. This is the first report of SpFMRFamide in S. pharaonis and the results may contribute to future studies of neuropeptide evolution or may prove useful for the development of aquaculture methods for this cuttlefish species.
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