HAX-1 regulates SERCA2a oxidation and degradation

Area of Science:

• Cardiovascular Biology
• Cellular Stress Response
• Molecular Cardiology

Background:

• Ischemia/reperfusion (I/R) injury causes heart dysfunction and cell death.
• Hematopoietic lineage substrate-1-associated protein X-1 (HAX-1) shows protective effects, but its endogenous role is unclear due to early lethality in knockout models.

Purpose of the Study:

• To investigate the function of endogenous HAX-1 in the adult heart, particularly in the context of I/R injury.
• To elucidate the molecular mechanisms by which HAX-1 influences cardiac function and survival during I/R.

Main Methods:

• Generation of a cardiac-specific and inducible HAX-1 deficient mouse model.
• Assessment of cardiac function, infarct size, and cardiomyocyte survival following I/R injury.
• Analysis of sarco/endoplasmic reticulum Ca-ATPase 2a (SERCA2a) levels, degradation pathways, and reactive oxygen species (ROS) production.
• Investigation of the role of NADPH oxidase 4 (NOX4) and apocynin treatment.

Main Results:

• Cardiac-specific HAX-1 deficiency worsened contractile recovery and increased infarct size after I/R injury.
• Ablation of HAX-1 led to increased SERCA2a degradation and enhanced ROS production, particularly at the sarcoplasmic reticulum.
• HAX-1 overexpression improved recovery and maintained SERCA2a levels, while NOX4 inhibition abrogated the detrimental effects of HAX-1 deficiency.
• HAX-1 interacts with NOX4, suggesting a role in regulating oxidative stress and SERCA2a stability.

Conclusions:

• Endogenous HAX-1 plays a critical role in protecting the heart against I/R injury.
• HAX-1 regulates SERCA2a degradation, likely through modulation of oxidative stress mediated by NOX4.
• These findings highlight HAX-1's importance in calcium homeostasis and cell survival pathways during cardiac stress.