Inflammation-induced PINCH expression leads to actin depolymerization and mitochondrial mislocalization in neurons.

BACKGROUND: Diseases and disorders with a chronic neuroinflammatory component are often linked with changes in brain metabolism. Among neurodegenerative disorders, people living with human immunodeficiency virus (HIV) and Alzheimer's disease (AD) are particularly vulnerable to metabolic disturbances, but the mechanistic connections of inflammation, neurodegeneration and bioenergetic deficits in the central nervous system (CNS) are poorly defined. The particularly interesting new cysteine histidine-rich-protein (PINCH) is nearly undetectable in healthy mature neurons, but is robustly expressed in tauopathy-associated neurodegenerative diseases including HIV infection and AD. Although robust PINCH expression has been reported in neurons in the brains of patients with HIV and AD, the molecular mechanisms and cellular consequences of increased PINCH expression in CNS disease remain largely unknown.

METHODS: We investigated the regulatory mechanisms responsible for PINCH protein-mediated changes in bioenergetics, mitochondrial subcellular localization and bioenergetic deficits in neurons exposed to physiological levels of TNFα or the HIV protein Tat. Changes in the PINCH-ILK-Parvin (PIP) complex association with cofilin and TESK1 were assessed to identify factors responsible for actin depolymerization and mitochondrial mislocalization. Lentiviral and pharmacological inhibition experiments were conducted to confirm PINCH specificity and to reinstate proper protein-protein complex communication.

RESULTS: We identified MEF2A as the PINCH transcription factor in neuroinflammation and determined the biological consequences of increased PINCH in neurons. TNFα-mediated activation of MEF2A via increased cellular calcium induced PINCH, leading to disruption of the PIP ternary complex, cofilin activation by TESK1 inactivation, and actin depolymerization. The disruption of actin led to perinuclear mislocalization of mitochondria by destabilizing the kinesin-dependent mitochondrial transport machinery, resulting in impaired neuronal metabolism. Blocking TNFα-induced PINCH expression preserved mitochondrial localization and maintained metabolic functioning.

CONCLUSIONS: This study reported for the first time the mechanistic and biological consequences of PINCH expression in CNS neurons in diseases with a chronic neuroinflammation component. Our findings point to the maintenance of PINCH at normal physiological levels as a potential new therapeutic target for neurodegenerative diseases with impaired metabolisms.