A potential antiapoptotic regulation: The interaction of heat shock protein 70 and apoptosis‐inducing factor mitochondrial 1 during heat stress and aestivation in sea cucumber

Abstract

The sea cucumber (Apostichopus japonicus) has become a good model organism for studying environmentally induced aestivation in marine invertebrates. A characteristic feature of aestivation in this species is the degeneration of the intestine. In the current study, we hypothesized that energy conservation and cytoprotective strategies need to be coordinated in the intestine to ensure long-term survival during aestivation, and there was potential relationship between heat shock protein 70 (HSP70) and apoptosis-inducing factor mitochondrial 1 (AIFM1) during extreme environmental stress. AIFM1 is a bifunctional flavoprotein that is involved in the caspase-independent activation of apoptosis. The gene and protein expression profiles of AjAIFM1 and AjHSP70 in intestinal tissue during aestivation were analyzed and results showed an inverse correlation between them, AjAIFM1 being suppressed during aestivation whereas AjHSP70 was strongly upregulated. Comparable responses were also seen when intestinal cells were isolated and analyzed in vitro for responses to heat stress at 25°C (a water temperature typical during aestivation), compared with 15°C control cells. Combined with co-immunoprecipitation studies in vivo and in vitro, our results suggested that AjHSP70 protein may have potential interaction with AjAIFM1. To determine the influence of heat stress on apoptotic rate of intestinal cells, we also assessed the DNA fragmentation by terminal deoxynucleotide transferase-mediated dUTP nick-end labeling assay, and results also supported a potential antiapoptotic response in sea cucumber during heat stress. This type of cytoprotective mechanism could be used to preserve the existing cellular components during long-term aestivation in sea cucumber.

Apoptosis-Inducing Factor 2 (AIF-2) Mediates a Caspase-Independent Apoptotic Pathway in the Tropical Sea Cucumber (Holothuria leucospilota)

“…Based on their widespread existence in various species, from invertebrates to humans [ 18 , 19 , 31 , 32 ], AIFs have been proposed to have an ancient and conserved pyridine nucleotide-disulfide oxidoreductase domain (Pyr_redox domain), which could generate superoxide rather than exhibit antioxidant activity [ 5 ]. Our current study found that Hl AIF-2 contained a Pyr_redox_2 domain and a deduced C-terminal NLS but lacked a recognizable MLS ( Figure 1 A).…”

“…Similarly, the intestine was the tissue with the highest expression level of AIF mRNA in Pacific white shrimps [ 18 ]. Previous studies showed that HSP70 could inhibit the nuclear translocation of AIFM1 during hibernation and thermal stimulation in A. japonicus , indicating a potential antiapoptotic response in the intestinal cells of sea cucumbers [ 19 ]. On the other hand, AIF-2 is reported to be involved in neural differentiation during embryonic development in vertebrates [ 37 , 38 ].…”

“…In crustacean mud crabs and Pacific white shrimps, AIF participates in the immune response against white spot syndrome virus (WSSV) infection by inducing apoptosis of haemocytes [ 17 , 18 ]. However, knowledge is limited regarding caspase-independent apoptotic pathways in echinoderms, except in a case reported for the sea cucumber Apostichopus japonicus , in which AIF-1 could mediate apoptosis induced by heat stress with a negatively correlated expression of heat shock protein 70 (HSP70) [ 19 ].…”

MiR-200-3p Is Potentially Involved in Cell Cycle Arrest by Regulating Cyclin A during Aestivation in Apostichopus japonicus

“…RR420) with the AjCA specific primer pairs (Table 1). β-tubulin (TBB, PIK103) was selected as an internal control and had been previously validated as being unchanged during A. japonicus aestivation in an initial study of reference gene stability [31]. β-actin (ACTB, PIK61412.1) was also selected as another internal control, which was mainly to ensure the constant expression of an internal control and made the results more stable and accurate.…”

Expression analysis of genes involved in TLR signalling pathway under temperature stress in sea cucumber Apostichopus japonicus

“…The aestivating A. japonicus is marked with intestinal atrophy along with alteration of microbiota and impairment of intestinal mucosa integrity. These changes will exaggerate the functions of TLR signalling pathways in intestinal inflammation and apoptosis (Wang, Li, Chen, Storey, & Wang, ). Arousal process is similar to the regeneration of intestine combined with the recovery of function and normal metabolism (Su et al, ; Sun, Yang, Chen, Ma, & Lin, ).…”