Biology subjects

Akimzhanov, A. M.

Publications and source records attributed to Akimzhanov, A. M..

6 recordsLinked to original sources

bioRxiv2026

DHHC3-dependent S-Acylation of CRY1 regulates its subcellular localization and repressor function in the circadian clock

The circadian clock is essential for maintaining cellular homeostasis and physiological fitness. At the molecular level, core clock proteins function via transcriptional-translational feedback loops in the cellular oscillator, and are highly regulated by post-translational modifications. Our unbiased screening of core clock proteins revealed that Cryptochrome 1 (CRY1), the central transcriptional repressor in the circadian clock, undergoes a novel post-translational modification known as S-acylation. We show that this reversible lipidation of CRY1 is required for its nuclear import and interaction with key clock components. Further, we mapped four cysteine residues as CRY1 S-acylation sites and identified DHHC3 as the primary protein acyltransferase for CRY1. Importantly, loss of CRY1 S-acylation, either via cysteine mutagenesis or genetic deletion of DHHC3, impaired CRY1 repressor function and consequently cellular circadian rhythms, suggesting that dynamic S-acylation couples cytoplasmic regulation of CRY1 and its transcriptional repressor function in the nucleus. Together, our findings identify S-acylation as a previously unknown post-translational modification of CRY1 critical for circadian clock function and establish DHHC3 as a pivotal circadian regulatory enzyme. Targeting CRY1 S-acylation or its regulatory enzymes may constitute an innovative therapeutic approach against clock-associated diseases.

biochemistry↗

bioRxiv2025

DHHC21 is a STIM1 protein S-acyltransferase that modulates immune function in vivo

Depletion of calcium from ER stores leads to the activation of calcium channels on the plasma membrane. This process is termed store-operated calcium entry (SOCE). The proteins STIM1 and STIM2 function as ER calcium sensors, and upon store depletion, they undergo a conformational change that allows them to bind to and gate Orai calcium channels on the plasma membrane. We have shown that both Orai1 and STIM1 are dynamically S-acylated after store depletion, which is required for SOCE. These results suggest the requirement of a calcium-activated protein S-acyltransferase such as DHHC21. Here, we show that DHHC21 is essential for SOCE in vitro and in vivo. Using the depilated mouse model that expresses DHHC21 but can no longer be activated by calcium, we show that DHHC21 activation is required for STIM1 S-acylation and subsequent calcium entry. Plasma membrane-localized DHHC21 is dynamically recruited into Orai1/STIM1 puncta upon store depletion, where it physically binds to STIM1. Finally, we show that depilated mice phenocopy many aspects of autoimmune lymphoproliferative syndrome (ALPS), including defective Fas-mediated calcium release, T cell death, neutropenia, and increased serum vitamin B12 levels. These results suggest that dynamic S-acylation has underappreciated and expansive roles in second messenger signaling and immune system function. Targeting DHHC21 may be therapeutically beneficial for ALPS and diseases associated with deregulated activation of STIM1, such as tubular aggregate myopathy and Stormorken syndrome.

immunology↗

bioRxiv2022

Dynamic S-acylation of STIM1 is required for store-operated Ca 2+ entry

Many cell surface stimuli cause calcium release from endoplasmic reticulum (ER) stores to regulate cellular physiology. Upon ER calcium store depletion, the ER-resident protein STIM1 physically interacts with plasma membrane protein Orai1 to induce calcium release-activated calcium (CRAC) currents that conduct calcium influx from the extracellular milieu. Although the physiological relevance of this process is well established, the mechanism supporting the assembly of these proteins is incompletely understood. Earlier we demonstrated a previously unknown post-translational modification of Orai1 with long chain fatty acids, known as S-acylation. We found that S-acylation of Orai1 is dynamically regulated in a stimulus-dependent manner and essential for its function as a calcium channel. Here we show that STIM1 is also rapidly and transiently S-acylated at cysteine 437 upon ER calcium store depletion. S-acylation of STIM1 is required for the assembly of STIM1 into puncta with Orai1 and full CRAC channel function. Together with the S-acylation of Orai1, our data suggest that stimulus-dependent S-acylation of CRAC channel components Orai1 and STIM1 is a critical mechanism facilitating CRAC channel assembly and function.

cell biology↗

bioRxiv2020

Regulation of T cell receptor signaling by protein acyltransferase DHHC21

S-acylation - reversible post-translational lipidation of cysteine residues - is emerging as an important regulatory mechanism in T cell signaling. Dynamic S-acylation is critical for protein recruitment into the T cell receptor complex and initiation of the subsequent signaling cascade. However, the enzymatic control of protein S-acylation in T cells remains poorly understood. Here, we report a previously uncharacterized role of DHHC21, a member of the mammalian family of DHHC protein acyltransferases, in regulation of the T cell receptor pathway. We found that loss of DHHC21 prevented S-acylation of key T cell signaling proteins, resulting in disruption of the early signaling events and suppressed expression of T cell activation markers. Furthermore, downregulation of DHHC21 prevented activation and differentiation of naive T cells into effector subtypes. Together, our study provides the first direct evidence that DHHC protein acyltransferases can play an essential role in regulation of T cell-mediated immunity.

cell biology↗

bioRxiv2019

Aggregated and hyperstable damage-associated molecular patterns are released during ER stress to modulate immune function

Chronic ER stress occurs when protein misfolding in the ER lumen remains unresolved despite activation of the unfolded protein response. We have shown that traumatic injury such as a severe burn leads to chronic ER stress in vivo leading to systemic inflammation which can last for more than a year. The mechanisms linking chronic ER stress to systemic inflammatory responses is not clear. Here we show that induction of chronic ER stress leads to the release of known and novel damage-associated molecular patterns (DAMPs). The secreted DAMPs are aggregated and markedly protease resistant. ER stress-derived DAMPs activate dendritic cells which are then capable of polarizing naive T cells. Our findings indicate that induction of chronic ER stress may lead to the release of hyperstable DAMPs into the circulation resulting in persistent systemic inflammation and adverse outcomes.

cell biology↗

bioRxiv2018

The palmitoyl acyltransferase DHHC5 mediates beta-adrenergic signaling in the heart by targeting Gα proteins and G protein-coupled receptor kinase 2

S-palmitoylation is a reversible posttranslational modification that plays an important role in regulating protein localization, trafficking, and stability. Recent studies have shown that some proteins undergo extremely rapid palmitoylation/depalmitoylation cycles after cellular stimulation supporting a direct signaling role for this posttranslational modification. Here we investigated whether {beta}-adrenergic stimulation of cardiomyocytes led to stimulus-dependent palmitoylation of downstream signaling proteins. We found that {beta}-adrenergic stimulation led to increased Gs and Gi palmitoylation. The kinetics of palmitoylation was temporally consistent with the downstream production of cAMP and positive inotropic responses. Additionally, we identified for the first time that G protein-coupled receptor kinase 2 (GRK2) is a palmitoylated protein in cardiomyocytes. The kinetics of GRK2 palmitoylation were distinct from those observed with Gs and Gi after {beta}-adrenergic stimulation. Knockdown of the plasma membrane-localized palmitoyl acyltransferase DHHC5 revealed that this enzyme is necessary for palmitoylation of Gs, Gi, and GRK2 and functional responses downstream of {beta}-adrenergic stimulation. Our results reveal that DHHC5 activity is required for signaling downstream of {beta}-adrenergic receptors.

cell biology↗