Biology subjects

xu, x.

Publications and source records attributed to xu, x..

7 recordsLinked to original sources

bioRxiv2026

Heterotrimeric G protein αi2 Sequesters RasGAP to Control Neutrophil Sensitivity and Chemotaxis

G protein-coupled receptors (GPCRs) direct neutrophil chemotaxis through heterotrimeric G proteins, yet the downstream effectors of the predominant Gai isoform, Gai2, remain incompletely defined. Here we identify the Ras GTPase-activating protein CAPRI (RASA4) as a functional effector of Gai2 that links GPCR signaling to Ras adaptation. Using AlphaFold3-based structural modeling and binding free-energy calculations and experimental verification, we reveal that constitutively active and structurally altered Gai2 mutants (Q205L and T182A) exhibit enhanced binding to CAPRI. Neutrophils expressing these mutants display elevated basal Ras activity, heightened sensitivity to chemoattractant, and improved chemotaxis in low- or subsensitive-concentration gradients. However, these cells exhibit excessive Ras activation and impaired chemotaxis at high, saturating chemoattractant concentrations, while maintaining near-normal responses at intermediate concentrations. These results reveal an upward shift in the concentration range for efficient chemotaxis. Our findings not only establish a previously unrecognized Gai2-CAPRI signaling axis that tunes Ras adaptation but also define a mechanism by which heterotrimeric G proteins calibrate leukocyte navigation across diverse chemoattractant gradients.

immunology↗

bioRxiv2025

PLCg2 Controls Neutrophil Sensitivity through Calcium Oscillation and Gates Chemoattractant Concentration Range for Chemotaxis

The connection between calcium oscillation and cell sensitivity is poorly understood. Calcium oscillation is triggered either spontaneously or upon receptor-ligand binding. The cytosolic [Ca2+] increase during calcium oscillation is initiated from Ca2+ release from the intracellular stores through the phospholipase C (PLC)-derived inositol 1,4,5-trisphosphate (IP3). Here, we show that neutrophils lacking PLC{gamma}2 (plcg2kd) display impaired spontaneous calcium oscillation and chemoattractant-induced calcium response, decreased membrane targeting of CAPRI (a RasGAP), and subsequent increased activations of Ras and its effectors, such as PI3K{gamma} activation and actin polymerization. More importantly, plcg2kd neutrophils sense and respond to chemoattractant at a subsensitive chemoattraction. Taken together, our results demonstrate that PLC{gamma}2 mediates spontaneous calcium oscillation, contributes to chemoattractant-triggered calcium response, controls neutrophil sensitivity through membrane targeting of CAPRI, and gates chemoattractant concentration range for neutrophil chemotaxis. HighlightsO_LINeutrophils lacking PLC{gamma}2 (plcg2kd) shows impaired spontaneous or GPCR-mediated Ca2+ oscillation. C_LIO_LIplcg2kd neutrophils display attenuated membrane targeting of CAPRI, a key negative regulator of Ras signaling and basal activity of neutrophils. C_LIO_LIplcg2kd neutrophils display an increased sensitivity and activation of GPCR-mediated signaling pathways. C_LIO_LIplcg2kd neutrophils display chemoattractant concentration-dependent alteration of chemotaxis behavior. C_LI

cell biology↗

bioRxiv2023

A glutamatergic DRN-VTA pathway for neuropathic pain and comorbid depression-like behavior modulation

Chronic pain causes both physical suffering and comorbid mental disorders such as depression. However, the neural circuits and molecular mechanisms underlying these maladaptive behaviors remain elusive. Here, we report a pathway from vesicular glutamate transporter3 neurons in the dorsal raphe nucleus to dopamine neurons in the ventral tegmental area (VGluT3DRN[->]DAVTA), of which population activity in response to innocuous mechanical stimuli and sucrose consumption, is respectively inhibited and attenuated by chronic neuropathic pain. Mechanistically, neuropathic pain dampens VGluT3DRN[->]DAVTA glutamatergic transmission and DAVTA neural excitability. VGluT3DRN[->]DAVTA activation alleviates neuropathic pain and comorbid depression-like behavior (CDB) by releasing glutamate, which subsequently promotes DA release in the nucleus accumbens medial shell (NAcMed) and produces analgesia and antidepressant effects via D2 and D1 receptors, respectively. In addition, VGluT3DRN[->]DAVTA inhibition produces pain-like hypersensitivity and depression-like behavior in healthy mice. These findings reveal a novel VGluT3DRN[->]DAVTA[->]D2/D1NAcMed pathway in establishing and modulating chronic pain and comorbid depressive-like behavior.

neuroscience↗

bioRxiv2020

GPCR-mediated Activation of PLCg2 Initiates Dysregulated Recruitment of Neutrophils in Cold-induced Urticaria in PLAID Patients

The current dogma is that chemoattractants G protein coupled receptors (GPCRs) activate {beta} phospholipase C (PLC{beta}) while receptor tyrosine kinases (RTKs) activate {gamma} phospholipase C (PLC{gamma}). Here, we show that chemoattractant/GPCR-mediated membrane recruitment of PLC{gamma}2 constitutes GPCR-mediated phospholipase C (PLC) signaling and is essential for neutrophil polarization and migration during GPCR-mediated chemotaxis. In response to a chemoattractant stimulation, cells lacking PLC{gamma}2 (plcg2kd) displayed altered dynamics of diacylglycerol (DAG) production and calcium response; increased Ras/PI3K/Akt activation; elevated GSK3 phosphorylation and cofilin activation; impaired dynamics of actin polymerization; and consequently defects in cell polarization and migration during chemotaxis. At low temperature, neutrophils expressing the gain-of-function mutant of PLC{gamma}2 ({Delta}686) displayed better chemotaxis than the cells expressing wild-type PLC{gamma}2. The study provides a molecular mechanism for the dysregulated recruitment and activation of neutrophils in cold-induced urticaria in PLC{gamma}2-associated antibody deficiency and immune dysregulation (PLAID) patients bearing gain-of-function mutations of PLC{gamma}2.

immunology↗

bioRxiv2020

Ras Inhibitor CAPRI Enables Neutrophils to Chemotax Through a Higher-Concentration Range of Gradients

Neutrophils sense and migrate through an enormous range of chemoattractant gradients through adaptation. Here, we reveal that, in human neutrophils, Calcium-promoted Ras inactivator (CAPRI) locally controls the GPCR-stimulated Ras adaptation. Human neutrophils lacking CAPRI (caprikd) exhibit chemoattractant-induced non-adaptive Ras activation; significantly increased phosphorylation of AKT, GSK3/3{beta}, and cofilin; and excessive actin polymerization. caprikd cells display defective chemotaxis in response to high-concentration gradients but exhibit improved chemotaxis in low- or subsensitive-concentration gradients of various chemoattractants as a result of their enhanced sensitivity. Taken together, our data reveal that CAPRI controls GPCR activation-mediated Ras adaptation and lowers the sensitivity of human neutrophils so that they are able to chemotax through a higher concentration range of chemoattractant gradients. Significance StatementNeutrophils provide first-line host defense by migrating through chemoattractant gradients to the sites of inflammation. Inappropriate recruitment and mis-regulated activation of neutrophils contribute to tissue damage and cause autoimmune and inflammatory disease. One fascinating feature of chemotactic neutrophils is their ability to migrate through an enormous concentration range of chemoattractant gradients (10-9 [~] 10-5 M) through "adaptation," in which cells no longer respond to the present stimuli, but remain sensitive to stronger stimuli. The inhibitory mechanism largely remains elusive, although many molecules of the excitatory signaling pathway have been identified. Our study reveals, for the first time, that the inhibitory component, CAPRI, is essential for both the sensitivity and the GPCR-mediated adaptation of human neutrophils.

cell biology↗

bioRxiv2019

Group Similarity Constraint Functional Brain Network Estimation for Mild Congititive Impairment Classification

Functional brain network (FBN) provides an effective biomarker for understanding brain activation patterns, which also improve the diagnostic criteria for neurodegenerative diseases or the information transmission of brain. Unfortunately, despite its efficiency, FBN still suffers several challenges for accurately estimate the biological meaningful or discriminative FBNs, under the poor quality of functional magnetic resonance imaging (fMRI) data as well as the limited understanding of human brain. Hence, there still a motivation to alleviate those issues above, it is currently still an open field to discover. In this paper, a novel FBN estimation model based on group similarity constraints is proposed. In particular, we extend the FBN estimation model to the tensor form and incorporate the trace-norm regularizer for formulating the group similarity constraint. In order to verify the proposed method, we conduct experiments on identifying Mild Cognitive Impairments (MCIs) from normal controls (NCs) based on the estimated FBNs. The experimental results illustrated that the proposed method can construct a more discriminative brain network. Consequently, we achieved an 91.97% classification accuracy which outperforms the baseline methods. The post hoc analysis further shown more biologically meaningful functional brain connections obtained by our proposed method.

bioinformatics↗

bioRxiv2018

Biolistic transformation of Haematococcus pluvialis with constructs based on the flanking sequences of its endogenous alpha tubulin gene

The complete sequence information of the alpha tubulin (tub) genes was obtained from both Haematococcus pluvialis NIES144 and SCCAP K0084., Putative transcriptional elements and polyadenylation signals were identified respectively in their 5 and 3 flanking regions. Three selection cassettes of tub/aadA, tub/hyr and tub/ble with 3 different antibiotic-resistant genes fused between the 5 and 3 flanking sequences of the tub gene were constructed and utilized for biolistic transformation of H.pluvialis. Antibiotic resistant transformants were obtained in the bombardments with the tub/aadA cassette in 2 strains. It was found that, the foreign tub/aadA DNA could be completely transferred and inherited in their genome through non-homologous recombination. Moreover, transcripts of the insert and spectinomycin resistance were identified. Transformation efficiencies up to 3x10-5 per g DNA could be obtained in H.pluvialis NIES144 or SCCAP K0084 through utilization of a culture with a high percentage of flagellate cells and by optimizing bombarding protocol. The presented selection marker and optimized transforming procedures in this report should strengthen the platform technology for genetical manipulation and modification of H.pluvialis.

molecular biology↗