Dysfunction of LSD-1 induces JNK signaling pathway-dependent abnormal development of thorax and apoptosis cell death in Drosophila melanogaster

Depletion of lipid storage droplet-1 delays endoreplication progression and induces cell death in Drosophila salivary gland

Perilipins are evolutionarily conserved from insects to mammals. Drosophila lipid storage droplet-1 (LSD-1) is a lipid storage droplet membrane surface-binding protein family member and a counterpart to mammalian perilipin 1 and is known to play a role in lipolysis. However, the function of LSD-1 during specific tissue development remains under investigation. This study demonstrated the role of LSD-1 in salivary gland development. Knockdown of Lsd-1 in the salivary gland was established using the GAL4/UAS system. The third-instar larvae of knockdown flies had small salivary glands containing cells with smaller nuclei. The null mutant Drosophila also showed the same phenotype. The depletion of LSD-1 expression induced a delay of endoreplication due to decreasing CycE expression and increasing DNA damage. Lsd-1 genetically interacted with Myc in the third-instar larvae. These results demonstrate that LSD-1 is involved in cell cycle and cell death programs in the salivary gland, providing novel insight into the effects of LSD-1 in regulating salivary gland development and the interaction between LSD-1 and Myc.

Dysfunction of lipid storage droplet-2 suppresses endoreplication and induces JNK pathway-mediated apoptotic cell death in Drosophila salivary glands

The lipid storage droplet-2 (LSD-2) protein of Drosophila is a homolog of mammalian perilipin 2, which is essential for promoting lipid accumulation and lipid droplet formation. The function of LSD-2 as a regulator of lipolysis has also been demonstrated. However, other LSD-2 functions remain unclear. To investigate the role of LSD-2, we performed tissue-specific depletion in the salivary glands of Drosophila using a combination of the Gal4-upstream activating sequence system and RNA interference. LSD-2 depletion inhibited the entry of salivary gland cells into the endoreplication cycle and delayed this process by enhancing CycE expression, disrupting the development of this organ. The deficiency of LSD-2 expression enhanced reactive oxygen species production in the salivary gland and promoted JNK-dependent apoptosis by suppressing dMyc expression. This phenomenon did not result from lipolysis. Therefore, LSD-2 is vital for endoreplication cell cycle and cell death programs.

Notum palmitoleoyl-protein carboxylesterase regulates Fas cell surface death receptor-mediated apoptosis via the Wnt signaling pathway in colon adenocarcinoma

Colon adenocarcinoma (COAD) is one of the most common types of malignancy and accounts for >3 million deaths worldwide each year. The present study aimed to evaluate the role of notum palmitoleoyl-protein carboxylesterase (NOTUM) in in vivo and in vitro, and to identify the relationship between NOTUM and the apoptosis of COAD. Moreover, the present study aimed to investigate whether NOTUM regulated Fas cell surface death receptor (FAS)-mediated apoptosis was affected by the Wnt signaling pathway. Gene expression profiling interactive analysis (GEPIA) was used to predict the potential function of NOTUM. Western blotting and reverse transcription-quantitative PCR were conducted to detect the protein and mRNA expression levels of NOTUM in different tissues or cell lines. The occurrence and development of COAD was detected after NOTUM knockdown lentivirus administration. The apoptosis of COAD was also observed. SKL2001 was applied to examine whether the role of NOTUM was regulated by Wnt. GEPIA analysis demonstrated that NOTUM expression in COAD tumor tissue was higher compared with in normal tissues. Pair-wise gene correlation analysis identified a potential relationship between NOTUM and Wnt. NOTUM protein and mRNA expression levels in colon carcinoma tissues and RKO cells were increased. NOTUM knockdown lentivirus serves a role in inhibiting COAD development by reducing tumor proliferation, reducing tumor size, and increasing the level of apoptosis in vitro and in vivo. Moreover, NOTUM could increase apoptosis in COAD, which was regulated by FAS, and SKL2001 blocked the progress of apoptosis after NOTUM regulation by NOTUM knockdown lentivirus in vitro and in vivo. Collectively, the present results suggested that NOTUM may be able to regulate the apoptosis of COAD, and that Wnt may be the down-stream target signaling of NOTUM in apoptosis.

Role of Serotonin Transporter in Eye Development of Drosophila melanogaster

Serotonin transporter (SerT) in the brain is an important neurotransmitter transporter involved in mental health. However, its role in peripheral organs is poorly understood. In this study, we investigated the function of SerT in the development of the compound eye in Drosophila melanogaster. We found that SerT knockdown led to excessive cell death and an increased number of cells in S-phase in the posterior eye imaginal disc. Furthermore, the knockdown of SerT in the eye disc suppressed the activation of Akt, and the introduction of PI3K effectively rescued this phenotype. These results suggested that SerT plays a role in the healthy eye development of D.melanogaster by controlling cell death through the regulation of the PI3K/Akt pathway.