Fadel, F. | Search bioRxiv

bioRxiv2025

Engineering Infrared Light Detection in Blind Human Retina Using Ultrasensitive Human TRPV1 Channels

Engineering infrared light sensitivity in the blind human retina could restore visual function in patients with regional retinal degeneration. However, current approaches are complex and contain non-human biological components. Using rational protein design we engineered human TRPV1 channels ({Delta}786-840) with temperature sensitivity shifted from 45 to 41{degrees}C that enabled near-infrared light- induced heat activation of mammalian cells at close to physiological temperatures. When expressed in ganglion cells of human retinal explants, {Delta}786-840 TRPV1 generated robust spiking responses to brief near-infrared light-induced temperature transients. Additionally, increasing intensity of radiation evoked graded responses correlating with increasing firing frequencies. Unlike previous approaches that used non-human TRPV1 channels, which risk immune reactions and a multicomponent system that poses barriers to clinical implementation, this single component human-derived approach eliminates immunogenicity concerns, addressing a major challenge to clinical translation, and allow gene delivery using adeno-associated viral vectors.

bioengineering↗

bioRxiv2021

Digital control of c-di-GMP in E. coli balances population-wide developmental transitions and phage sensitivity

Nucleotide-based signaling molecules (NSMs) are widespread in bacteria and eukaryotes, where they control important physiological and behavioral processes. In bacteria, NSM-based regulatory networks are highly complex, entailing large numbers of enzymes involved in the synthesis and degradation of active signaling molecules. How the converging input from multiple enzymes is transformed into robust and unambiguous cellular responses has remained unclear. Here we show that Escherichia coli converts dynamic changes of c-di-GMP into discrete binary signaling states, thereby generating heterogeneous populations with either high or low c-di-GMP. This is mediated by an ultrasensitive switch protein, PdeL, which senses the prevailing cellular concentration of the signaling molecule and couples this information to c-di-GMP degradation and transcription feedback boosting its own expression. We demonstrate that PdeL acts as a digital filter that facilitates precise developmental transitions, confers cellular memory, and generates functional heterogeneity in bacterial populations to evade phage predation. Based on our findings, we propose that bacteria apply ultrasensitive regulatory switches to convert dynamic changes of NSMs into binary signaling modes to allow robust decision-making and bet-hedging for improved overall population fitness.

microbiology↗