Monitoring AKT activity and targeting in live tissue and disease contexts using a real-time Akt-FRET biosensor mouse

A DNA Fishhook Electrochemical Sensor Based on a Potassium Ferricyanide-Mediated Dual-Signal-Correlation Enhanced Electrocatalysis Reaction for a Simultaneous and Correlation Assay of Multiple Biomarkers

Simultaneous detection and correlation analysis of multiple biomarkers in a single run are crucial to improving the detection specificity and indicate disease progression, but they remain a challenge. Herein, we propose a DNA fishhook electrochemical sensor based on the potassium ferricyanide-mediated dual-signal correlation enhanced electrocatalysis reaction (DEER). The designed T-shaped DNA fishhook scaffold has two "hooks" to recruit their respective "fish" (targets) with the help of the "fishing bait" (signal probes, Sp), resulting in the different targets and Sp being specifically captured by the DNA fishhook to the electrode interface, respectively. The proposed DEER not only effectively improves the detection sensitivity without introducing nucleic acid amplification but also can reflect the logical correlation between the targets. As proof of principle, the DNA fishhook sensor was successfully applied in the simultaneous detection of two related gene sequences of SARS-CoV-2 and the active-state assay of the PI3K/AKT signaling pathway. In general, our DNA fishhook sensor provides a meaningful potential tool for the sensitive simultaneous detection and correlation analysis of multiple targets.

Genetically encoded biosensor for fluorescence lifetime imaging of PTEN dynamics in the intact brain

The phosphatase and tensin homolog (PTEN) is a vital protein that maintains an inhibitory brake for cellular proliferation and growth. Accordingly, PTEN loss-of-function mutations are associated with a broad spectrum of human pathologies. Despite its importance, there is currently no method to directly monitor PTEN activity with cellular specificity within intact biological systems. Here we describe the development of a FRET-based biosensor using PTEN conformation as a proxy for the PTEN activity state, for two-photon fluorescence lifetime imaging microscopy. We identify a point mutation that allows the monitoring of PTEN activity with minimal interference to endogenous PTEN signaling. We demonstrate imaging of PTEN activity in cell lines, intact Caenorhabditis elegans and in the mouse brain. Finally, we develop a red-shifted sensor variant that allows us to identify cell-type-specific PTEN activity in excitatory and inhibitory cortical cells. In summary, our approach enables dynamic imaging of PTEN activity in vivo with unprecedented spatial and temporal resolution.

Pharmacodynamics of Akt drugs revealed by a kinase-modulated bioluminescent indicator

Measuring pharmacodynamics (PD)-the biochemical effects of drug dosing-and correlating them with therapeutic efficacy in animal models is crucial for the development of effective drugs but traditional PD studies are labor and resource intensive. Here we developed a kinase-modulated bioluminescent indicator (KiMBI) for rapid, noninvasive PD assessment of Akt-targeted drugs, minimizing drug and animal use. Using KiMBI, we performed a structure-PD relationship analysis on the brain-active Akt inhibitor ipatasertib by generating and characterizing two novel analogs. One analog, ML-B01, successfully inhibited Akt in both the brain and the body. Interestingly, capivasertib, ipatasertib and ML-B01 all exhibited PD durations beyond their pharmacokinetic profiles. Furthermore, KiMBI revealed that the PD effects of an Akt-targeted proteolysis-targeting chimera degrader endured for over 3 days. Thus, bioluminescence imaging with Akt KiMBI provides a noninvasive and efficient method for in vivo visualization of the PD of Akt inhibitors and degraders.

Characterizing heterogeneous single-cell dose responses computationally and experimentally using threshold inhibition surfaces and dose-titration assays

Single cancer cells within a tumor exhibit variable levels of resistance to drugs, ultimately leading to treatment failures. While tumor heterogeneity is recognized as a major obstacle to cancer therapy, standard dose-response measurements for the potency of targeted kinase inhibitors aggregate populations of cells, obscuring intercellular variations in responses. In this work, we develop an analytical and experimental framework to quantify and model dose responses of individual cancer cells to drugs. We first explore the connection between population and single-cell dose responses using a computational model, revealing that multiple heterogeneous populations can yield nearly identical population dose responses. We demonstrate that a single-cell analysis method, which we term a threshold inhibition surface, can differentiate among these populations. To demonstrate the applicability of this method, we develop a dose-titration assay to measure dose responses in single cells. We apply this assay to breast cancer cells responding to phosphatidylinositol-3-kinase inhibition (PI3Ki), using clinically relevant PI3Kis on breast cancer cell lines expressing fluorescent biosensors for kinase activity. We demonstrate that MCF-7 breast cancer cells exhibit heterogeneous dose responses with some cells requiring over ten-fold higher concentrations than the population average to achieve inhibition. Our work reimagines dose-response relationships for cancer drugs in an emerging paradigm of single-cell tumor heterogeneity.