Biology subjects

Ishigami, K.

Publications and source records attributed to Ishigami, K..

4 recordsLinked to original sources

bioRxiv2025

CGK733 binds to adenine nucleotide translocator 2 and modulates mitochondrial function and protein translation

Chemical genetics is a powerful strategy for dissecting biological mechanisms, and a crucial step in this approach is to identify the molecular target responsible for a compounds activity. CGK733, a compound with anti-proliferative activity, was once reported as an ATM/ATR inhibitor, although this activity has been debated, and its target and mode of action have remained unclear. Here, we show that CGK733 inhibits cell-cycle progression and global protein translation. Affinity purification identified adenine nucleotide translocator 2 (ANT2) as the primary target. CGK733 blocked ATP export from mitochondria and induced proton leak, thereby shifting ATP production from mitochondrial respiration to glycolysis and perturbing the TCA cycle. These mitochondrial alterations were accompanied by inactivation of the mTOR pathway and mild activation of the integrated stress response, resulting in translational inhibition. Collectively, our findings demonstrate that CGK733 acts mainly through ANT2-dependent mitochondrial modulation, revealing a mechanistic link between mitochondrial bioenergetics and translational control.

biochemistry↗

bioRxiv2025

Evolution in spatiotemporal infection patterns of Burkholderia sensu lato lineages in the gut of Riptortus pedestris

Many plants and animals form specific symbioses with microorganisms, relying on bidirectional interactions between hosts and bacteria. However, the knowledge about the evolution of symbiont traits enabling such specificity remains very limited. The bean bug Riptortus pedestris acquires Caballeronia from environmental soil and harbors it in its gut symbiotic organ. This bug-Caballeronia symbiosis is an ideal model to clarify the evolutionary process of symbiotic bacteria because members of their outgroups, such as Paraburkholderia and Pandoraea, can also colonize the host symbiotic organ but are outcompeted when co-inoculated with the native symbiont, Caballeronia. In this study, mechanisms underpinning the competitiveness of Caballeronia inside the insect gut were investigated. First, comparative microscopy revealed that Caballeronias success in the gut is largely attributed to its ability to migrate rapidly to the M4 region through chemotaxis, wherein a cheA insertion mutant showed significantly delayed infection speed and lower competitiveness against wild-type. In addition, Paraburkholderia and Pandoraea frequently formed biofilm-like aggregates in the midgut, which could delay their colonization. By contrast, Caballeronia formed no biofilm-like aggregates, at least inside the insect gut. This study reveals that Caballeronia symbiont has evolved traits like chemotaxis and reaction against AMP to establish an efficient and exclusive symbiotic relationship with their bean bug host. Although the genetic and molecular bases of the chemotaxis and the cell aggregates remain unclear, it is strongly suggested that the dynamic gain and loss of these traits enables Caballeronia to specifically associate with the insect host, R. pedestris. ImportanceRiptortus pedestris, a major soybean pest in East Asia, acquires symbiotic bacteria from the environment every generation, yet its gut is consistently and specifically colonized by Caballeronia species. The evolutionary traits that underlie this strong symbiotic specificity remain poorly understood. Here, we demonstrate that Caballeronia insecticola has acquired two key traits: positive chemotaxis toward the symbiotic organ and tolerance to host-derived antimicrobial peptides (AMPs). Using comparative colonization assays with wild-type, chemotaxis-deficient mutants, a non-symbiotic sister group, and their common ancestor, we show that these adaptations enable Caballeronia to outcompete other bacteria within the host gut. Our findings provide direct evidence that specific ecological and behavioral traits contribute to the establishment of exclusive symbiotic associations, shedding light on how symbiotic specificity can evolve even in horizontally transmitted systems. This work offers novel insights into the evolutionary dynamics of host-microbe interactions.

microbiology↗

bioRxiv2025

Bacteria break through one-micrometer-square passages by flagellar wrapping

Confined spaces are omnipresent in the micro-environments, including soil aggregates and intestinal crypts, yet little is known about how bacteria behave under such conditions where movement is challenging due to limited diffusion. Stinkbug symbiont Caballeronia insecticola navigates a narrow gut passage about one micrometer in diameter to reach the stinkbugs symbiotic organ. Here, we developed a microfluidic device mimicking the hosts sorting organ, wherein bacterial cells are confined in a quasi-one-dimensional fashion, and revealed that this bacterium wraps flagellar filaments around its cell body like a screw thread to control fluid flow and generate propulsion for smooth and directional movement in narrow passages. Physical simulations and genetic experiments revealed that hook flexibility is essential for this wrapping; increasing hook rigidity impaired both wrapping motility and infectivity. Thus, flagellar wrapping likely represents an evolutionary innovation, enabling bacteria to break through confined environments using their motility machinery.

microbiology↗

bioRxiv2023

Hundreds of antimicrobial peptides create a selective barrier for insect gut symbionts

The spatial organization of gut microbiota is crucial for the functioning of the gut ecosystem, although the mechanisms that organize gut bacterial communities in microhabitats are only partially understood. The gut of the insect Riptortus pedestris has a characteristic microbiota biogeography with a multispecies community in the anterior midgut and a mono-specific bacterial population in the posterior midgut. We show that the posterior midgut region produces massively hundreds of specific antimicrobial peptides (AMPs), the Crypt-specific Cysteine-Rich peptides (CCRs) that have membrane-damaging antimicrobial activity against diverse bacteria but posterior midgut symbionts have elevated resistance. We determined by transposon-sequencing the genetic repertoire in the symbiont Caballeronia insecticola to manage CCR stress, identifying different independent pathways, including novel AMP-resistance pathways unrelated to known membrane homeostasis functions as well as cell envelope functions. Mutants in the corresponding genes have reduced capacity to colonize the posterior midgut, demonstrating that CCRs create a selective barrier and resistance is crucial in gut symbionts. Moreover, once established in the gut, the bacteria differentiate into a CCR-sensitive state, suggesting a second function of the CCR peptide arsenal in protecting the gut epithelia or mediating metabolic exchanges between the host and the gut symbionts. Our study highlights the evolution of an extreme diverse AMP family that contributes to establish and control the gut microbiota.

microbiology↗