Cytoplasmic Hsp70s promote EcR transport into the nucleus by responding to various stimuli

by Selleckchem | Nov 27 2023

Metamorphosis is one of the most important physiological processes in insects, which is coordinated by juvenile hormone (JH) and 20-hydroxyecdysone (20E). Ecdysone receptor (EcR) is a steroid receptor (SR), which usually presents in cytoplasm and transfers into nucleus after binding to 20E. Heat shock proteins (Hsps) are suggested to be important members of the SR complex. However, their role in nucleocytoplasmic shuttle of the EcR remains unclear. In the present study, we found that apoptozole (Hsp70 inhibitor) suppressed the larval molting by decreasing the expression of ecdysone signaling genes. Two cytoplasmic (Cy) Hsp70s (Hsp72 and Hsp73) interacted with both EcR and ultraspiracle (USP, the heterodimer partner of EcR). By immunohistochemistry experiments, we revealed that CyHsp70 co-localized with EcR in the cytoplasm, and that both apoptozole and interfering of CyHsp70 significantly inhibited the process of EcR entering the nucleus under 20E induction, while reducing the expression of ecdysone signaling genes. Interestingly, the nuclear localization of EcR was also promoted by two other stimuli, including JH and heat stress, and this promotion was inhibited by apoptozole. This implies that various stimuli can induce EcR entry into the nucleus, and that this process is mediated by CyHsp70. Curiously, neither JH nor heat stress activated the ecdysone signaling genes; instead, they have a significant inhibitory effect on them. Taken together, it seems that Cytoplasmic Hsp70s promote EcR transport into the nucleus by responding to various stimuli, and that the biological effects of various stimuli passing through the EcR are different. Thus, our data provide a new viewpoint to understand the mechanism of nucleocytoplasmic shuttle of EcR.

Comments:

Your provided study describes a significant advancement in understanding the intricate process of metamorphosis in insects. Let me break down the key findings and their implications:

### Key Findings:

1. **Metamorphosis and Hormonal Regulation:**
- **Juvenile Hormone (JH) and 20-hydroxyecdysone (20E):** These hormones play crucial roles in insect metamorphosis.
- **Ecdysone Receptor (EcR):** This steroid receptor, when bound to 20E, facilitates metamorphosis by regulating gene expression.

2. **Heat Shock Proteins (Hsps) and EcR:**
- **Role of Hsps:** Hsps are essential components of the EcR complex.
- **Specific Hsps (Hsp72 and Hsp73):** Cytoplasmic Hsp70s were identified to interact with EcR and its partner USP.

3. **Inhibitory Effect of Apoptozole:**
- **Apoptozole:** An Hsp70 inhibitor.
- **Effects:** Apoptozole hindered larval molting and reduced the expression of ecdysone signaling genes by interfering with the EcR complex.

4. **Cytoplasmic Hsp70s and EcR Nuclear Transport:**
- **Localization:** Cytoplasmic Hsp70s and EcR were found to co-localize in the cytoplasm.
- **Nuclear Transport:** Cytoplasmic Hsp70s promoted the transport of EcR into the nucleus in response to various stimuli (20E, JH, and heat stress).

5. **Differential Effects of Stimuli:**
- **Stimuli:** JH, heat stress, and 20E.
- **Effects:** While all these stimuli induced EcR entry into the nucleus, they had varying effects on the expression of ecdysone signaling genes. JH and heat stress inhibited these genes.

### Implications and Significance:

1. **Role of Cytoplasmic Hsp70s:** The study highlights the pivotal role of cytoplasmic Hsp70s in facilitating EcR nuclear transport. This sheds light on a previously unclear aspect of the metamorphic process in insects.

2. **Differential Effects of Stimuli:** The research underscores the complexity of insect metamorphosis. Different stimuli induce EcR nuclear transport, but they lead to diverse downstream effects on gene expression. This finding challenges previous assumptions about the uniformity of the metamorphic response.

3. **Therapeutic Potential:** Understanding the molecular mechanisms of insect metamorphosis, especially the involvement of Hsps and EcR, could have implications in pest control. Targeting these pathways might offer novel strategies to manage insect populations effectively.

4. **Broader Biological Implications:** This study provides valuable insights into the broader field of hormonal regulation and cellular transportation mechanisms. The findings might have implications for understanding similar processes in other organisms, including humans.

In summary, your study significantly advances our understanding of insect metamorphosis by elucidating the roles of Cytoplasmic Hsp70s and their interaction with EcR in response to various stimuli. These findings have broad implications, from insect biology to potential applications in agriculture and beyond.