Advanced Optogenetic-Based Biosensing and Related Biomaterials

The ability to stimulate mammalian cells with light, brought along by optogenetic control, has significantly broadened our understanding of electrically excitable tissues. Backed by advanced (bio)materials, it has recently paved the way towards novel biosensing concepts supporting bio-analytics applications transversal to the main biomedical stream. The advancements concerning enabling biomaterials and related novel biosensing concepts involving optogenetics are reviewed with particular focus on the use of engineered cells for cell-based sensing platforms and the available toolbox (from mere actuators and reporters to novel multifunctional opto-chemogenetic tools) for optogenetic-enabled real-time cellular diagnostics and biosensor development. The key advantages of these modified cell-based biosensors concern both significantly faster (minutes instead of hours) and higher sensitivity detection of low concentrations of bioactive/toxic analytes (below the threshold concentrations in classical cellular sensors) as well as improved standardization as warranted by unified analytic platforms. These novel multimodal functional electro-optical label-free assays are reviewed among the key elements for optogenetic-based biosensing standardization. This focused review is a potential guide for materials researchers interested in biosensing based on light-responsive biomaterials and related analytic tools.

Retrograde Signaling: Understanding the Communication between Organelles

Understanding how cell organelles and compartments communicate with each other has always been an important field of knowledge widely explored by many researchers. However, despite years of investigations, one point—and perhaps the only point that many agree on—is that our knowledge about cellular-signaling pathways still requires expanding. Chloroplasts and mitochondria (because of their primary functions in energy conversion) are important cellular sensors of environmental fluctuations and feedback they provide back to the nucleus is important for acclimatory responses. Under stressful conditions, it is important to manage cellular resources more efficiently in order to maintain a proper balance between development, growth and stress responses. For example, it can be achieved through regulation of nuclear and organellar gene expression. If plants are unable to adapt to stressful conditions, they will be unable to efficiently produce energy for growth and development—and ultimately die. In this review, we show the importance of retrograde signaling in stress responses, including the induction of cell death and in organelle biogenesis. The complexity of these pathways demonstrates how challenging it is to expand the existing knowledge. However, understanding this sophisticated communication may be important to develop new strategies of how to improve adaptability of plants in rapidly changing environments.

HIV-1 Is a Poor Inducer of Innate Immune Responses

ABSTRACT Effective host immune responses against viral infection rely on the detection of the virus, activation of downstream signaling pathways, and the secretion of interferons (IFNs) and other cytokines. Many viruses can potently stimulate these responses, whereas the immune response against human immunodeficiency virus type 1 (HIV-1) remains relatively less well characterized. Here we show that HIV-1 infection with reporter viruses does not activate sensing pathways in cell lines and primary cells that are otherwise responsive to foreign nucleic acids. After entry into cells, reverse transcription and reporter expression occur without the virus ever being detected by cellular sensors or stimulating an interferon response. Using multiple methods, including the use of reporter cell lines for type I IFN and NF-κB pathway activation, quantifying mRNA levels for IFN-stimulated genes (ISGs), and assaying for markers of innate immune activation, we show that single-round pseudotyped HIV-1-based reporter viruses fail to induce innate immune responses. IMPORTANCE Human immunodeficiency virus type 1 (HIV-1) continues to be a major burden to human health worldwide. How infected cells recognize and respond to HIV-1 infection is important in order to better understand the biology of the virus and the cellular pathways activated upon infection and to identify potential targets that interfere with viral replication. In this study, we investigated innate immune responses of different cell types following infection with single-cycle (replication-defective) HIV-1 reporter virus. We report that infection with a commonly used HIV-1 strain (lacking the env, nef, and vpr genes) does not measurably activate cellular defense mechanisms and that the virus is able to avoid recognition by cellular sensors.