Characterization of interaction between C-domain on HIV-1 gp41 and the putative receptor protein p62

Role of p62/SQSTM1 beyond autophagy: a lesson learned from drug-induced toxicity in vitro

BACKGROUND AND PURPOSE

SQSTM1/p62 is a multifunctional, stress-induced, scaffold protein involved in multiple cellular processes including autophagic clearance, regulation of inflammatory responses and redox homeostasis. Its altered function has been associated with different human pathologies, such as neurodegenerative, metabolic and bone diseases (down-regulation), and cancerogenesis (up-regulation). However, its role in the off-target effects of clinically used drugs is still not understood.

EXPERIMENTAL APPROACH

We evaluated the expression of p62 in cultured Hep3B cells and their derived ρ° cells (lacking mitochondria), along with markers of autophagy and mitochondrial dysfunction. The effects of efavirenz were compared with those of known pharmacological stressors, rotenone, thapsigargin and CCCP, and we also used transient silencing with siRNA and p62 overexpression. Western blotting, quantRT-PCR and fluorescence microscopy were used to assay these effects and their underlying mechanisms.

KEY RESULTS

In Hep3B cells, efavirenz augmented p62 protein content, an effect not observed in the corresponding ρ° cells. p62 up-regulation followed enhanced SQSTM1 expression mediated through the transcription factor CHOP/DDIT3, while other well-known regulators (NF-kB and Nrf2) were not involved. Inhibition of autophagy with 3MA or with transient silencing of Atg5 did not affect SQSTM1 expression in efavirenz-treated cells while p62 overexpression ameliorated the deleterious effect of efavirenz on cell viability.

CONCLUSION AND IMPLICATIONS

In our model, p62 exerted a specific, autophagy-independent role and protected against efavirenz-induced mitochondrial ROS generation and activation of the NLRP3 inflammasome. These findings add to the multifunctional nature of p62 and may help to understand the off-target effects of clinically useful drugs.

Spying on HIV with SPR

The application of surface plasmon resonance (SPR)-based optical biosensors has contributed extensively to our understanding of functional aspects of HIV. SPR biosensors allow the analysis of real-time interactions of any biomolecule, be it protein, nucleic acid, lipid, carbohydrate or small molecule, without the need for intrinsic or extrinsic probes. As such, the technology has been used to analyze molecular interactions associated with every aspect of the viral life cycle, from basic studies of binding events occurring during docking, replication, budding and maturation to applied research related to vaccine and inhibitory drug development. Along the way, SPR biosensors have provided a unique and detailed view into the inner workings of HIV.

Survey of the year 2001 commercial optical biosensor literature

We have assembled references of 700 articles published in 2001 that describe work performed using commercially available optical biosensors. To illustrate the technology's diversity, the citation list is divided into reviews, methods and specific applications, as well as instrument type. We noted marked improvements in the utilization of biosensors and the presentation of kinetic data over previous years. These advances reflect a maturing of the technology, which has become a standard method for characterizing biomolecular interactions.