Biology subjects

Tran, M. V.

Publications and source records attributed to Tran, M. V..

3 recordsLinked to original sources

bioRxiv2026

A membrane-permeable small molecule biosensor accesses intractable cells and animals without genetic manipulation

Fluorescent biosensors have proven valuable for revealing the spatio-temporal dynamics of protein conformation in live cells and animals. The great majority of biosensors are genetically encoded, but genetic encoding is difficult or impossible to apply in many cases, including cells or animals with poorly understood genomes, no DNA, or sensitive to manipulation. Using biosensors without genetic manipulation could greatly simplify studies in animals, expand the range of accessible organisms, and ultimately enable application in humans. Here we explore using a membrane-permeable small molecule as a fluorescent biosensor. The drug trifluoperazine, which binds only to the active conformation of calmodulin, was covalently linked to an environment-sensing merocyanine dye to create CaMero, a biosensor of calmodulin activation. Simple incubation of CaMero in the extracellular medium, or injection in the tail vein of mice, led to sensitive real time reporting of calmodulin activity. The dye underwent a 12-fold change in fluorescence intensity upon binding to activated calmodulin, revealing waves of activation in peristaltic intestine, localization and kinetics of calmodulin activation during serum stimulation in fibroblasts, and localized activation in the single-celled marine protist foraminifera.

cell biology↗

bioRxiv2023

MAP9/MAPH-9 supports axonemal microtubule doublets and modulates motor movement

Microtubule doublets (MTDs) are a well conserved compound microtubule structure found primarily in cilia. However, the mechanisms by which MTDs form and are maintained in vivo remain poorly understood. Here, we characterize microtubule-associated protein 9 (MAP9) as a novel MTD-associated protein. We demonstrate that C. elegans MAPH-9, a MAP9 homolog, is present during MTD assembly and localizes exclusively to MTDs, a preference that is in part mediated by tubulin polyglutamylation. Loss of MAPH-9 caused ultrastructural MTD defects, dysregulated axonemal motor velocity, and perturbed cilia function. As we found that the mammalian ortholog MAP9 localized to axonemes in cultured mammalian cells and mouse tissues, we propose that MAP9/MAPH-9 plays a conserved role in supporting the structure of axonemal MTDs and regulating ciliary motors.

cell biology↗

bioRxiv2020

Centriole-less pericentriolar material serves as a microtubule organizing center at the base of C. elegans sensory cilia

During mitosis in animal cells, the centrosome acts as a microtubule organizing center (MTOC) to assemble the mitotic spindle. MTOC function at the centrosome is driven by proteins within the pericentriolar material (PCM), however the molecular complexity of the PCM makes it difficult to differentiate the proteins required for MTOC activity from other centrosomal functions. We used the natural spatial separation of PCM proteins during mitotic exit to identify a minimal module of proteins required for centrosomal MTOC function in C. elegans. Using tissue specific degradation, we show that SPD-5, the functional homolog of CDK5RAP2, is essential for embryonic mitosis while SPD-2/CEP192 and PCMD-1, which are essential in the zygote, are dispensable. Surprisingly, although the centriole is known to be degraded in the ciliated sensory neurons in C. elegans [1-3], we find evidence for "centriole-less PCM" at the base of cilia and use this structure as a minimal testbed to dissect centrosomal MTOC function. Super-resolution imaging revealed that this PCM inserts inside the lumen of the ciliary axoneme and directly nucleates the assembly of dendritic microtubules towards the cell body. Tissue-specific degradation in ciliated sensory neurons revealed a role for SPD-5 and the conserved microtubule nucleator {gamma}-TuRC, but not SPD-2 or PCMD-1, in MTOC function at centriole-less PCM. This MTOC function was in the absence of regulation by mitotic kinases, highlighting the intrinsic ability of these proteins to drive microtubule growth and organization and further supporting a model that SPD-5 is the primary driver of MTOC function at the PCM.

cell biology↗