Biology subjects

Mullick, S.

Publications and source records attributed to Mullick, S..

3 recordsLinked to original sources

bioRxiv2026

Glutamylated vimentin proteoform identified by a synthetic binder links to epithelial-mesenchymal plasticity

Cytoskeletal protein expression and filament dynamics change significantly during cell state transitions. However, post-translational modifications of cytoskeletal proteins during these transitions have rarely been described. Here, using a synthetic glutamylation-binder (SB2B49) selected against a bi-glutamylated peptide epitope, we identify a distinct pool of glutamylated vimentin filaments. We demonstrate that vimentin glutamylation is enzymatically added by tubulin tyrosine ligase-like (TTLLs) and removed by cytosolic carboxypeptidases (CCPs). Mass spectrometry and mutagenesis reveal that glutamylation occurs on specific vimentin residues. We find that glutamylated vimentin levels are dynamically modulated during epithelial-mesenchymal plasticity. During collective migration in scratch-wound assays, glutamylated vimentin filaments are transiently depleted at the wound edge, a process controlled by canonical glutamylation writer-erasers. Our findings reveal a new layer of vimentin regulation via glutamylation and establish the glutamylation-binder as a valuable tool for exploring the diversity of vimentin proteoforms and glutamylation modifications in both physiological and pathological contexts.

cell biology↗

bioRxiv2026

Tubulin glycylation regulates microtubule-protein interactions that are key for ciliary stability and trafficking

Tubulin glycylation, a cilia-specific posttranslational modification is emerging as a potentially key regulator of ciliary axonemal microtubules. However, insights into the functional consequences of glycylation have remained limited. Here, using in vitro reconstitution assays with unmodified or custom-glycylated tubulin, we provide a systematic mechanistic analysis of glycylation-dependent regulation of motors and microtubule-associated proteins. Our studies highlight that glycylation selectively enhances ciliary kinesin-2 motility while reducing kinesin-1 activity, suggesting a role in promoting efficient intraflagellar transport along axonemal microtubules. Moreover, glycylation protects microtubules from decay by suppressing the activities of the depolymerase MCAK and severing enzyme spastin, thereby enhancing stability. Notably, this regulation is dependent on the proportion of glycylation on the microtubule surface, coupled with concomitant reduction of glutamylation. Thus, by generating microtubule surfaces with distinct biochemical states, we establish that combinatorial modification patterns define functional microtubule properties especially in cilia. Together, our findings provide the first comprehensive mechanistic framework for tubulin glycylation in regulating molecular motors and MAPs in cilia, establishing glycylation as a key determinant of motor selectivity and microtubule stability within the axoneme.

biochemistry↗

bioRxiv2025

IntAct-U-ExM: Ultrastructure Expansion microscopy of actin networks via an internally-tagged actin

Expansion microscopy (ExM) has revolutionized super-resolution imaging in cell biology due to its simple and inexpensive workflow. The use of ExM has revealed several novel insights into the nanoscale architectures of cellular protein complexes, especially the microtubule cytoskeleton in model and non-model systems. Despite tremendous progress in expansion microscopy protocols that preserve cellular ultrastructure (U-ExM), compatible probes for imaging actin isoforms with U-ExM are still lacking and have hindered the study of diverse actin isoforms and networks across model systems. Here, we use IntAct, an internally tagged actin that incorporates into cellular actin networks, to develop and optimize U-ExM of diverse actin network types in both yeast and mammalian cells. Using expression of ALFA-tagged IntAct variants in yeast and mammalian cells, we show robust visualization of actin patches, cables, and rings in yeast and diverse actin networks such as actin cortex, stress fibers, filopodia, lamellipodium in mammalian cells at improved resolution. We also detect transient nuclear actin filaments using IntAct-U-ExM underscoring the advantages offered by our approach to image understudied actin structures. Overall, we demonstrate the effectiveness of IntAct-U-ExM for performing super-resolution imaging of various actin structures in an isoform-specific manner and highlight the potential of IntAct to study the nanoscale organization of diverse actin cytoskeletal networks across species. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=76 SRC="FIGDIR/small/654030v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@169cd82org.highwire.dtl.DTLVardef@1334af3org.highwire.dtl.DTLVardef@7d9d43org.highwire.dtl.DTLVardef@dfc50b_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗