Biology subjects

Uttamapinant, C.

Publications and source records attributed to Uttamapinant, C..

4 recordsLinked to original sources

bioRxiv2026

aaRSID, an engineered pyrrolysyl-tRNA synthetase platform for multi-probe proximity proteomics

Proximity labeling (PL) methods utilize spatially targeted chemical or enzymatic generation of a diffusible, reactive intermediate to covalently tag neighboring proteins in living systems. Unlike other tools for studying molecular interactions, PL can detect transient protein relationships with high spatial and temporal sensitivity, allowing for insight into their roles in biological processes. However, current enzymatic PL tools, such as TurboID and APEX2, are limited by their substrate structure and chemistry, which can generate significant background and/or perturb cellular physiology. To address these limitations, we have developed aminoacyl-tRNA synthetase ID (aaRSID), a PL tool that leverages an engineered pyrrolysyl tRNA synthetase (PylRS) for proximity labeling of proteins. We chose PylRS because it can catalyze promiscuous lysine labeling in the absence of its cognate tRNA and utilize a variety of non-canonical amino acids (ncAAs) as substrates. Here, we demonstrate aaRSID's intrinsic proximity labeling activity, use directed evolution to improve this activity, and apply the improved mutant (aaRSID-Ma1.3) for subcellular proteomics and multiplexed imaging. Our work establishes aminoacyl-tRNA synthetases as a new PL enzyme class and introduces a versatile chemical platform for developing ncAA-derived probes to map cellular microenvironments, greatly expanding the applications possible of PL technology.

biochemistry↗

bioRxiv2024

NCBP1 electrophilic-stress signaling in the nucleus promotes alternatively-spliced S6K1 that dominantly inhibits global translation

Subcellular stress profoundly influences protein synthesis. However, both the nature of spatiotemporally restricted chemical cues and local protein responders to these cues remain elusive. Unlocking these mechanisms requires the ability to functionally map in living systems locale-specific stress-responder proteins and interrogate how chemical modification of each responder impacts proteome synthesis. We resolved this problem by integrating precision localized electrophile generation and genetic code expansion tools. Upon examination of four distinct subcellular locales, only nuclear-targeted electrophile stress stalled translation. We discovered that NCBP1--a nuclear-resident protein with multifaceted roles in eukaryotic mRNA-biogenesis--propagated this nuclear stress signal through a single cysteine (C436) from among its 19 conserved cysteines. This NCBP1(C436)-specific modification elicited alternative splicing of >250 genes. Mechanistically, global protein-synthesis stall was choreographed by impaired association between electrophile-modified NCBP1(C436) and SF3A1, an essential component of spliceosome, triggering the production of alternatively-spliced S6-kinase, whose expression was sufficient to dominantly inhibit protein translation. SummaryNuclear reactive electrophile stress suppresses translation via an unprecedented gain of function mechanism. First NCBP1 is labeled at one of its 19 cysteines. This triggers alternative S6K1 splicing, which is dominant negative for translation.

biochemistry↗

bioRxiv2020

Alt-RPL36 downregulates the PI3K-AKT-mTOR signaling pathway by interacting with TMEM24

Thousands of previously unannotated small and alternative open reading frames (alt-ORFs) have recently been revealed in the human genome, and hundreds are now known to be required for cell proliferation. Many alt-ORFs are co-encoded with proteins of known function in multicistronic human genes, but the functions of only a handful are currently known in molecular detail. Using a proteomic strategy for discovery of unannotated short open reading frames in human cells, we report the detection of alt-RPL36, a 148-amino acid protein co-encoded with and overlapping human RPL36 (ribosomal protein L36). Alt-RPL36 partially localizes to the endoplasmic reticulum, where it interacts with TMEM24, which transports the phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] precursor phosphatidylinositol from the endoplasmic reticulum to the plasma membrane. Knock-out of alt-RPL36 in HEK 293T cells increases PI(4,5)P2 levels in the plasma membrane, upregulates the PI3K-AKT-mTOR signaling pathway, and increases cell size. Four serine residues of alt-RPL36 are phosphorylated, and mutation of these four serines to alanine abolishes interaction with TMEM24 and, consequently, abolishes alt-RPL36 effects on PI3K signaling and cell size. These results implicate alt-RPL36 as a novel regulator of PI(4,5)P2 synthesis upstream of the PI3K-AKT-mTOR signaling pathway. More broadly, these results show that the alt-RPL36 transcript can express two sequence-independent polypeptides from overlapping ORFs that regulate the same process - protein synthesis - via different molecular mechanisms (PI3K signaling and ribosome composition), expanding our knowledge of the mechanisms by which multicistronic human genes function.

genomics↗

bioRxiv2018

A conformational sensor based on genetic code expansion reveals an autocatalytic component in EGFR activation

Epidermal growth factor receptor (EGFR) activation by growth factors (GFs) relies on dimerization and allosteric activation of its intrinsic kinase activity, resulting in trans-phosphorylation of tyrosines on its C-terminal tail. While structural and biochemical studies identified this EGF-induced allosteric activation, imaging collective EGFR activation in cells and molecular dynamics simulations pointed at additional catalytic EGFR activation mechanisms. To gain more insight in EGFR activation mechanisms in living cells, we developed a Forster Resonance Energy Transfer (FRET) based conformational EGFR indicator (CONEGI) using genetic code expansion that reports on conformational transitions in the EGFR activation loop. Comparing conformational transitions, self-association and auto-phosphorylation of CONEGI and its Y845F mutant revealed that Y845 phosphorylation induces a catalytically active conformation in EGFR monomers. This conformational transition depends on EGFR kinase activity and auto-phosphorylation on its C-terminal tail, generating a looped causality that leads to autocatalytic amplification of EGFR phosphorylation at low EGF dose.

molecular biology↗