Proteolytic activity of 26s proteasomes isolated from muscles of the tobacco hornworm, Manduca sexta: differences between surviving muscles and those undergoing developmentally programmed cell death

Effects of selected insecticidal substances on mRNA transcriptome in larvae of Apis mellifera

For the last decade, scientists have reported a loss of honeybee colonies. Multiple factors like parasites, pathogens and pesticides are dealt as possible drivers of honeybee losses. In particular, insecticides are considered as a major factor of pollinator poisoning. We applied sublethal concentrations of four insecticidal substances to honeybee larval food and analyzed the effects on transcriptome. The aim was to identify candidate genes indicating early negative impacts after application of insecticidal substances. Honeybee larvae were kept in-vitro under hive conditions (34-35 °C) and fed with dimethoate, fenoxycarb, chlorantraniliprole and flupyradifurone in sublethal concentrations between day 3-6 after grafting. Larvae at day 4, 6 and 8 were sampled and their transcriptome analyzed. By use of a RT-qPCR array differences in gene expression of selected gene families (immune system, development detoxification) were measured. Targets mainly involved in development, energy metabolism and the immune system were significantly affected by the insecticidal substances tested, selectively inducing genes of the detoxification system, immune response and nutritional stress.

Differential control of cell death and gene expression during two distinct phases of hormonally-regulated muscle death in the tobacco hawkmoth Manduca sexta

In larvae of the tobacco hawkmoth Manduca sexta, the intersegmental muscles (ISMs) span eight abdominal segments and represent the major muscle group. Following pupation, the ISMs in the first two and last two segments undergo programmed cell death (PCD), while the remaining four segments persist until the time of adult eclosion, when they too undergo PCD. ISM death at adult eclosion is initiated by a decline in the circulating ecdysteroid titer and requires de novo gene expression. In this study we have investigated the hormonal regulation and the patterns of gene expression that accompany both early and late ISM death. We find that distinct endocrine cues regulate these two periods of muscle death. Even though the middle segments of ISMs are exposed to the same endocrine environment as the adjacent cells that die following pupation, they do not express death-associated transcripts until they are specifically signaled to die following adult eclosion. These data indicate that subsets of homologous muscles appear to make segment-specific decisions to couple their endogenous cell death programs to distinctly different developmental cues. Nevertheless, once cell death is initiated, they utilize many of the same molecular components.

Role of proteasomes in cellular regulation

The 26S proteasome is the key enzyme of the ubiquitin-dependent pathway of protein degradation. This energy-dependent nanomachine is composed of a 20S catalytic core and associated regulatory complexes. The eukaryotic 20S proteasomes demonstrate besides several kinds of peptidase activities, the endoribonuclease, protein-chaperone and DNA-helicase activities. Ubiquitin-proteasome pathway controls the levels of the key regulatory proteins in the cell and thus is essential for life and is involved in regulation of crucial cellular processes. Proteasome population in the cell is structurally and functionally heterogeneous. These complexes are subjected to tightly organized regulation, particularly, to a variety of posttranslational modifications. In this review we will summarize the current state of knowledge regarding proteasome participation in the control of cell cycle, apoptosis, differentiation, modulation of immune responses, reprogramming of these particles during these processes, their heterogeneity and involvement in the main levels of gene expression.