The receptor for activated C kinase 1 (RACK1) mediating immune response in thick shell mussel Mytilus coruscus

Area of Science:

• Marine Biology
• Molecular Biology
• Immunology

Background:

• Receptor for activated C kinase 1 (RACK1) is an intracellular protein involved in diverse biological processes.
• RACK1 acts as an intracellular scaffold for protein kinase C (PKC) and other signaling molecules.
• Understanding RACK1's function in invertebrates like mollusks is crucial for deciphering immune responses.

Purpose of the Study:

• To identify and characterize a novel RACK1 gene (Mc-RACK1) in the thick shell mussel, Mytilus coruscus.
• To investigate the expression patterns of Mc-RACK1 in response to immune stimuli (LPS) and heavy metal exposure (copper).
• To elucidate the functional role of Mc-RACK1 in the mussel's immune and antioxidant defense systems.

Main Methods:

• Gene identification and sequence analysis of Mc-RACK1 from Mytilus coruscus.
• Quantitative real-time PCR (qRT-PCR) to analyze Mc-RACK1 gene expression in various tissues and under different stress conditions.
• RNA interference (RNAi) to silence Mc-RACK1 in haemocytes, followed by assessment of antioxidant enzyme activities (SOD, CAT).
• Reporter gene assays in HEK-293T cells to evaluate Mc-RACK1's effect on NF-κB and ISRE pathways.

Main Results:

• A novel RACK1 gene, Mc-RACK1, was identified, possessing conserved RACK1 domains including WD repeats and phosphorylation sites.
• Mc-RACK1 exhibited constitutive expression in all examined tissues, with significant upregulation in gills, haemocytes, and digestive glands upon LPS challenge.
• Copper exposure led to downregulated Mc-RACK1 expression in gills and haemocytes.
• Silencing Mc-RACK1 in haemocytes resulted in increased SOD and CAT activities, suggesting a role in antioxidant defense.
• Mc-RACK1 activation of NF-κB and ISRE reporters indicated its involvement in immune signaling pathways.

Conclusions:

• Mc-RACK1 is a key component of the immune system in Mytilus coruscus.
• Mc-RACK1 plays a significant role in the antioxidant defense mechanisms of mollusks.
• The findings highlight Mc-RACK1's involvement in mediating responses to both immunological challenges and environmental stressors like heavy metals.