Relevance of ineffective esophageal motility to striated esophageal muscle contraction: Studies with high-resolution manometry.

Striated esophageal muscle contraction (SEC) is important for pharyngeal swallowing and deglutition augmentation against aspiration. Its clinical relevance is unclear in patients with ineffective esophageal motility (IEM). In this study, we aimed to characterize and compare SEC in consecutive patients with and without IEM. All eligible patients were evaluated for SEC, primary and secondary peristalsis using high-resolution manometry (HRM) with one mid-esophageal injection port. Primary peristalsis was assessed with 10 5-mL liquid swallows and multiple rapid swallows (MRS), while secondary peristalsis was performed with rapid air injections of 20 mL. All peristatic parameters of HRM were measured, and SEC and its contractile integral (SECI) were evaluated. One hundred and forty patients (59.3% women, mean age 46.1 ± 13.1 years) were included. There was no difference in SECI between patients with and without IEM (p = 0.91). SECI was also similar between patients with and without secondary peristalsis for IEM (p = 0.63) or normal motility (p = 0.80). No difference in SECI was seen between patients with and without MRS for IEM (p = 0.55) or normal motility (p = 0.88). SECI was significantly higher in male patients than female patients in IEM patients (p = 0.01). SECI significantly correlated with age in patients with normal motility (r = -0.31, p = 0.01). Aging may have a negative impact on SEC in patients with normal motility, while gender difference in SECI occurs in IEM patients. Neither secondary peristalsis nor MRS influences SECI.

Molecular mechanisms of enteric neuropathies in high-fat diet feeding and diabetes.

BACKGROUND: Obesity and diabetes are associated with altered gastrointestinal function and with the development of abdominal pain, nausea, diarrhea, and constipation among other symptoms. The enteric nervous system (ENS) regulates gastrointestinal motility. Enteric neuropathies defined as damage or loss of enteric neurons can lead to motility disorders. PURPOSE: Here, we review the molecular mechanisms that drive enteric neurodegeneration in diabetes and obesity, including signaling pathways leading to neuronal cell death, oxidative stress, and microbiota alteration. We also highlight potential approaches to treat enteric neuropathies including antioxidant therapy to prevent oxidative stress-induced damage and the use of stem cells.

Prognostic factors for pediatric patients with severe intestinal motility disorders: a single institution's experience.

PURPOSE: To identify the prognostic factors for pediatric severe intestinal motility disorder (IMD). METHODS: We reviewed the medical records of patients with severe IMD, who required total parenteral nutrition (TPN) for ≥ 60 days at our institution between April, 1984 and March, 2023, examining their characteristics to identify prognostic factors. RESULTS: The types of IMD in the 14 patients enrolled in this study were as follows: isolated hypoganglionosis (IHG, n = 6), extensive aganglionosis (EAG: n = 6), and chronic idiopathic intestinal pseudo-obstruction (CIIP, n = 2). There was no significant difference in mortality among the three types of severe IMD. Weaning-off TPN and the use of the colon were not significant prognostic factors, but cholestasis was a significant prognostic factor (p = 0.005). There was a high mortality rate (50%), with the major causes of death being intestinal failure-associated liver disease (IFALD) following hepatic failure, and catheter-related blood stream infection (CRBSI). One IHG patient underwent small bowel transplantation but died of acute rejection. CONCLUSION: Severe IMD is still associated with a high mortality rate and cholestasis predicts the prognosis. Thus, preventing or improving IFALD and CRBSI caused by long-term TPN is important for reducing the mortality rate.

Perioperative Gastrointestinal Myoelectric Activity Measurement Using Wireless External Patches.

BACKGROUND: Stomach, small intestine, and colon have distinct patterns of contraction related to their function to mix and propel enteric contents. In this study, we aim to measure gut myoelectric activity in the perioperative course using external patches in an animal model. METHODS: Four external patches were placed on the abdominal skin of female Yucatan pigs to record gastrointestinal myoelectric signals for 3 to 5 d. Pigs subsequently underwent anesthesia and placement of internal electrodes on stomach, small intestine, and colon. Signals were collected by a wireless transmitter. Frequencies associated with peristalsis were analyzed for both systems for 6 d postoperatively. RESULTS: In awake pigs, we found frequency peaks in several ranges, from 4 to 6.5 cycles per minute (CPM), 8 to 11 CPM, and 14 to 18 CPM, which were comparable between subjects and concordant between internal and external recordings. The possible effect of anesthesia during the 1 or 2 h before surgical manipulation was observed as a 59% (±36%) decrease in overall myoelectric activity compared to the immediate time before anesthesia. The myoelectrical activity recovered quickly postoperatively. Comparing the absolute postsurgery activity levels to the baseline for each pig revealed higher overall activity after surgery by a factor of 1.69 ± 0.3. CONCLUSIONS: External patch measurements correlated with internal electrode recordings. Anesthesia and surgery impacted gastrointestinal myoelectric activity. Recordings demonstrated a rebound phenomenon in myoelectric activity in the postoperative period. The ability to monitor gastrointestinal tract myoelectric activity noninvasively over multiple days could be a useful tool in diagnosing gastrointestinal motility disorders.

Integrative Effects of Transcutaneous Electrical Acustimulation and Autonomic-Endocrine Mechanisms on Postprocedural Recovery in Patients With Endoscopic Retrograde Cholangio-Pancreatography.

OBJECTIVES: This study aimed to investigate the integrative effects and mechanisms of transcutaneous electrical acustimulation (TEA) on postprocedural recovery from endoscopic retrograde cholangio-pancreatography (ERCP). MATERIALS AND METHODS: A total of 86 patients for elective ERCP were randomly ordered to receive TEA (n = 43) at acupoints PC6 and ST36 or Sham-TEA (n = 43) at sham points from 24 hours before ERCP (pre-ERCP) to 24 hours after ERCP (PE24). Scores of gastrointestinal (GI) motility-related symptoms and abdominal pain, gastric slow waves, and autonomic functions were recorded through the spectral analysis of heart rate variability; meanwhile, circulatory levels of inflammation cytokines of tumor necrosis factor-α (TNF-α) and interleukin (IL)-10 and GI hormones of motilin, ghrelin, cholecystokinin (CCK), and vasoactive intestinal peptide (VIP) were assessed by enzyme-linked immunosorbent assay. RESULTS: 1) TEA, but not Sham-TEA, decreased the post-ERCP GI motility-related symptom score (2.4 ± 2.6 vs 7.9 ± 4.6, p < 0.001) and abdominal pain score (0.5 ± 0.7 vs 4.1 ± 2.7, p < 0.001) at PE24, and decreased the post-ERCP hospital day by 20.0% (p ＜0.05 vs Sham-TEA); 2) TEA improved the average gastric percentage of normal slow waves and dominant frequency by 34.6% and 33.3% at PE24, respectively (both p < 0.001 vs Sham-TEA); 3) TEA, but not Sham-TEA, reversed the ERCP-induced increase of TNF-α but not IL-10 at PE24, reflected as a significantly lower level of TNF-α in the TEA group than in the Sham-TEA group (1.6 ± 0.5 pg/mL vs 2.1 ± 0.9 pg/mL, p ＜ 0.01); 4) compared with Sham-TEA, TEA increased vagal activity by 37.5% (p ＜ 0.001); and 5) TEA caused a significantly higher plasma level of ghrelin (1.5 ± 0.8 ng/ml vs 1.1 ± 0.7 ng/ml, p ＜ 0.05) but not motilin, VIP, or CCK than did Sham-TEA at PE24. CONCLUSION: TEA at PC6 and ST36 accelerates the post-ERCP recovery, reflected as the improvement in GI motility and amelioration of abdominal pain, and suppression of the inflammatory cytokine TNF-α may mediate through both autonomic and ghrelin-related mechanisms.

Biochemical characterization of paralyzed flagellum proteins A (PflA) and B (PflB) from Helicobacter pylori flagellar motor.

Motility by means of flagella plays an important role in the persistent colonization of Helicobacter pylori in the human stomach. The H. pylori flagellar motor has a complex structure that includes a periplasmic scaffold, the components of which are still being identified. Here, we report the isolation and characterization of the soluble forms of two putative essential H. pylori motor scaffold components, proteins PflA and PflB. We developed an on-column refolding procedure, overcoming the challenge of inclusion body formation in E. coli. We employed mild detergent sarkosyl to enhance protein recovery and n-dodecyl-N,N-dimethylamine-N-oxide (LDAO)-containing buffers to achieve optimal solubility and monodispersity. In addition, we showed that PflA lacking the ß-rich N-terminal domain is expressed in a soluble form, and behaves as a monodisperse monomer in solution. The methods for producing the soluble, folded forms of H. pylori PflA and PflB established in this work will facilitate future biophysical and structural studies aimed at deciphering their location and their function within the flagellar motor.

BolA-like protein (IbaG) promotes biofilm formation and pathogenicity of Vibrio parahaemolyticus.

Vibrio parahaemolyticus is a gram-negative halophilic bacterium widespread in temperate and tropical coastal waters; it is considered to be the most frequent cause of Vibrio-associated gastroenteritis in many countries. BolA-like proteins, which reportedly affect various growth and metabolic processes including flagellar synthesis in bacteria, are widely conserved from prokaryotes to eukaryotes. However, the effects exerted by BolA-like proteins on V. parahaemolyticus remain unclear, and thus require further investigation. In this study, our purpose was to investigate the role played by BolA-like protein (IbaG) in the pathogenicity of V. parahaemolyticus. We used homologous recombination to obtain the deletion strain ΔibaG and investigated the biological role of BolA family protein IbaG in V. parahaemolyticus. Our results showed that IbaG is a bacterial transcription factor that negatively modulates swimming capacity. Furthermore, overexpressing IbaG enhanced the capabilities of V. parahaemolyticus for swarming and biofilm formation. In addition, inactivation of ibaG in V. parahaemolyticus SH112 impaired its capacity for colonizing the heart, liver, spleen, and kidneys, and reduced visceral tissue damage, thereby leading to diminished virulence, compared with the wild-type strain. Finally, RNA-sequencing revealed 53 upregulated and 71 downregulated genes in the deletion strain ΔibaG. KEGG enrichment analysis showed that the two-component system, quorum sensing, bacterial secretion system, and numerous amino acid metabolism pathways had been altered due to the inactivation of ibaG. The results of this study indicated that IbaG exerts a considerable effect on gene regulation, motility, biofilm formation, and pathogenicity of V. parahaemolyticus. To the best of our knowledge, this is the first systematic study on the role played by IbaG in V. parahaemolyticus infections. Thus, our findings may lead to a better understanding of the metabolic processes involved in bacterial infections and provide a basis for the prevention and control of such infections.

Manometric Abnormalities in Patients With and Without Chronic Cough.

PURPOSE: This study examines the relationship between chronic cough and vagal hypersensitivity by measuring baseline esophageal motility, with interest in the upper esophageal sphincter (UES). MATERIALS AND METHODS: Patients undergoing workup for dysphagia were assigned to a chronic cough or control group based on self-reported symptoms. Differences in demographics, medical comorbidities, and high resolution esophageal manometry findings were obtained retrospectively. RESULTS: 62.5% of our cohort had chronic cough (30/48). There were no significant differences between the two groups with respect to sex, age, and race/ethnicity. Laryngopharyngeal reflux (LPR) was the only statistically significant predictor of CC (OR 74.04, p = 0.010). Cough patients had upper esophageal sphincter relaxation duration (734 ms) significantly longer than the non-cough patients (582 ms; p = 0.03), though both groups had similar upper esophageal mean basal pressure, mean residual pressure, relaxation time-to-nadir, and recovery time. No significant difference was found in the median intrabolus pressure and UES motility mean peak pressure between groups. CONCLUSION: Subtle differences in high-resolution manometry between patients with and without cough suggest, in line with previous studies, baseline alterations of upper esophageal function may manifest in patients with chronic cough through an undetermined mechanism that may include underlying vagal hypersensitivity. These findings encourage further manometric study examining the relationship between UES dysfunction and chronic cough.

Effects of 2,4,6-Trichloroanisole on the morphological development and motility of zebrafish.

2,4,6-Trichloroanisole (2,4,6-TCA), a compound with a characteristic earthy odor, is a common source of odorous pollutants in drinking water and wine. However, research on its biological toxicity is limited. In this study, we used zebrafish as an indicator model to investigate the effects of 2,4,6-TCA exposure on morphological development, oxidative stress, apoptosis, heart rate, blood flow, and motility. We found that exposure to 2,4,6-TCA resulted in significant spinal, tail, and cardiac deformities in zebrafish larvae and promoted a pronounced oxidative stress response and extensive cell apoptosis, notably in the digestive tract, head, spine, and heart, ultimately leading to significant reductions in zebrafish heart rate, blood flow, and motility. Moreover, these effects became more pronounced with an increase in the concentration of 2,4,6-TCA to which the zebrafish were exposed. Furthermore, qPCR analysis revealed that exposure to 2,4,6-TCA promoted significant changes in the expression levels of genes associated with oxidative stress, apoptosis, cardiac development, and the nervous system, particularly key genes (p53, apaf1, casp9, and casp3) in the mitochondrial apoptotic pathway, which were significantly upregulated. Similarly, we detected significant upregulation of ache gene expression. These findings indicated that exposure to 2,4,6-TCA resulted in the accumulation of reactive oxygen species in zebrafish, induced strong oxidative stress responses, and triggered lipid peroxidation and extensive cell apoptosis. Cellular apoptosis, which mitochondrial signaling pathways may mediate, has been found to lead to malformations in zebrafish embryos, resulting in significant reductions in cardiac function and motility. To our knowledge, this is the first systematic assessment of the toxicity of 2,4,6-TCA, and our findings provide an important reference for risk assessment and early warning of 2,4,6-TCA exposure.

On the generation of force required for actin-based motility.

The fundamental question of how forces are generated in a motile cell, a lamellipodium, and a comet tail is the subject of this note. It is now well established that cellular motility results from the polymerization of actin, the most abundant protein in eukaryotic cells, into an interconnected set of filaments. We portray this process in a continuum mechanics framework, claiming that polymerization promotes a mechanical swelling in a narrow zone around the nucleation loci, which ultimately results in cellular or bacterial motility. To this aim, a new paradigm in continuum multi-physics has been designed, departing from the well-known theory of Larché-Cahn chemo-transport-mechanics. In this note, we set up the theory of network growth and compare the outcomes of numerical simulations with experimental evidence.

Spontaneous enteric nervous system activity generates contractile patterns prior to maturation of gastrointestinal motility.

BACKGROUND: Spontaneous neuronal network activity is essential to the functional maturation of central and peripheral circuits, yet whether this is a feature of enteric nervous system development has yet to be established. Although enteric neurons are known exhibit electrophysiological properties early in embryonic development, no connection has been drawn between this neuronal activity and the development of gastrointestinal (GI) motility patterns. METHODS: We use ex vivo GI motility assays with newly developed unbiased computational analyses to identify GI motility patterns across mouse embryonic development. KEY RESULTS: We find a previously unknown pattern of neurogenic contractions termed "clustered ripples" that arises spontaneously at embryonic day 16.5, an age earlier than any identified mature GI motility patterns. We further show that these contractions are driven by nicotinic cholinergic signaling. CONCLUSIONS & INFERENCES: Clustered ripples are neurogenic contractile activity that arise from spontaneous ENS activity and precede all known forms of neurogenic GI motility. This earliest motility pattern requires nicotinic cholinergic signaling, which may inform pharmacology for enhancing GI motility in preterm infants.

Exploring the reticulo-ruminal motility pattern in goats through medical barium meal imaging technology.

The motility pattern of the reticulo-rumen is a key factor affecting feed intake, rumen digesta residence time, and rumen fermentation. However, it is difficult to study reticulo-ruminal motility using general methods owing to the complexity of the reticulo-ruminal structure. Thus, we aimed to develop a technique to demonstrate the reticulo-ruminal motility pattern in static goats. Six Xiangdong black goats (half bucks and half does, body weight 29.5 ± 1.0 kg) were used as model specimens. Reticulo-ruminal motility videos were obtained using medical barium meal imaging technology. Videos were then analyzed using image annotation and the centroid method. The results showed that reticulo-ruminal motility was divided into primary (stages I, II, III, and IV) and secondary contraction, and the movements of ruminal digesta depended on reticulo-ruminal motility. Our results indicated common motility between the ruminal dorsal sac and ruminal dorsal blind sac. We observed that stages I (3.92 vs. 3.21 s) (P < 0.01), II (4.81 vs. 4.23 s) (P < 0.01), and III (5.65 vs. 5.15 s) (P < 0.05); interval (53.79 vs. 50.95 s); secondary contraction time (10.5 vs. 10 s); and were longer, whereas stage IV appeared to be shorter in the bucks than in the does (7.83 vs. 14.67 s) (P < 0.01). The feasibility of using barium meal imaging technology for assessing reticulo-ruminal and digesta motility was verified in our study. We determined the duration of each stage of reticulo-ruminal motility and collected data on the duration and interval of each stage of ruminal motility in goats. This research provides new insights for the study of gastrointestinal motility and lays a solid foundation for the study of artificial rumen.

Downregulation of Fidgetin-Like 2 Increases Microglial Function: The Relationship Between Microtubules, Morphology, and Activity.

The microtubule cytoskeleton regulates microglial morphology, motility, and effector functions. The microtubule-severing enzyme, fidgetin-like 2 (FL2), negatively regulates cell motility and nerve regeneration, making it a promising therapeutic target for central nervous system injury. Microglia perform important functions in response to inflammation and injury, but how FL2 affects microglia is unclear. In this study, we investigated the role of FL2 in microglial morphology and injury responses in vitro. We first determined that the pro-inflammatory stimulus, lipopolysaccharide (LPS), induced a dose- and time-dependent reduction in FL2 expression associated with reduced microglial ramification. We then administered nanoparticle-encapuslated FL2 siRNA to knockdown FL2 and assess microglial functions compared to negative control siRNA and vehicle controls. Time-lapse live-cell microscopy showed that FL2 knockdown increased the velocity of microglial motility. After incubation with fluorescently labeled IgG-opsonized beads, FL2 knockdown increased phagocytosis. Microglia were exposed to low-dose LPS after nanoparticle treatment to model injury-induced cytokine secretion. FL2 knockdown enhanced LPS-induced cytokine secretion of IL-1α, IL-1ß, and TNFα. These results identify FL2 as a regulator of microglial morphology and suggest that FL2 can be targeted to increase or accelerate microglial injury responses.

Antispasmodic Activity of Light-Roasted Coffee Extract and Its Potential Use in Gastrointestinal Motility Disorders.

Antispasmodic agents are crucial in managing gastrointestinal motility disorders by modulating muscle contractions and reducing symptoms like cramping and diarrhea. This study investigated the antispasmodic potential of different coffee bean extracts, including light coffee (LC), medium coffee (MC), and dark coffee (DC), on ileum contractions induced by potassium chloride (KCl), and elucidated their mechanisms of action using in vitro isolated tissue techniques. The results demonstrated that all coffee extracts reduced spontaneous contractions of rat ileum tissue in a dose-dependent manner. Among these, LC showed the most significant reduction in ileum contractions, particularly at higher concentrations. The key findings reveal that LC at 5 mg/mL significantly reduced CaCl2-induced contractions in isolated rat ileum tissue, indicating that LC may inhibit calcium influx or interfere with calcium signaling pathways. The presence of nifedipine, propranolol, and N-nitro-L-arginine methyl ester (L-NAME) have been confirmed in their involvement; they block calcium influx and calcium channels and activate ß-adrenergic pathways as part of LC's mechanism of action. The presence of their active compounds, particularly chlorogenic acid and caffeine, likely contributes to the observed antispasmodic effects. These findings suggest that LC exerts its antispasmodic effects by targeting key mechanisms involved in muscle spasms and intestinal motility, providing a potential for managing such conditions.

The Motility of ß-Cyclodextrins Threaded on the Polyrotaxane Based Triblock Polymer and Its Influences on Mechanical Properties.

Polyrotaxane (PR) has garnered increasing attention due to its unique structure and exceptional performance. In this study, a polypseudorotaxane (PPR) initiator was prepared through the self-assembly of bromine-capped Pluronic F68 and ß-cyclodextrins (ß-CD) in water. Polyrotaxane-containing triblock copolymers (PR copolymers) were successfully synthesized by atom transfer radical polymerization (ATRP) of butyl methacrylate (BMA) using the PPR initiator in the presence of Cu(I)Br/PMDETA. The structure of the PR copolymers was thoroughly characterized using infrared spectroscopy (IR), proton nuclear magnetic resonance (1H NMR), and gel permeation chromatography (GPC). The mobility of ß-CD in the PR copolymers was demonstrated through dielectric measurements. Mechanical tests, including tensile strength assessments, thermal mechanical analysis, and dynamic mechanical analysis, confirmed the excellent mechanical properties and good processability of the PR copolymer, attributed to the PBMA blocks. Furthermore, the mechanical properties were found to be modulated by the motility of the threaded ß-CDs. Consequently, the superior mechanical properties and the high mobility of the threaded ß-CDs suggest promising potential for the as-prepared PR polymer in various advanced applications.

Brain Perception of Different Oils on Appetite Regulation: An Anorectic Gene Expression Pattern in the Hypothalamus Dependent on the Vagus Nerve.

(1) Background: We examined the effect of the acute administration of olive oil (EVOO), linseed oil (GLO), soybean oil (SO), and palm oil (PO) on gastric motility and appetite in rats. (2) Methods: We assessed food intake, gastric retention (GR), and gene expression in all groups. (3) Results: Both EVOO and GLO were found to enhance the rate of stomach retention, leading to a decrease in hunger. On the other hand, the reduction in food intake caused by SO was accompanied by delayed effects on stomach retention. PO caused an alteration in the mRNA expression of NPY, POMC, and CART. Although PO increased stomach retention after 180 min, it did not affect food intake. It was subsequently verified that the absence of an autonomic reaction did not nullify the influence of EVOO in reducing food consumption. Moreover, in the absence of parasympathetic responses, animals that received PO exhibited a significant decrease in food consumption, probably mediated by lower NPY expression. (4) Conclusions: This study discovered that different oils induce various effects on parameters related to food consumption. Specifically, EVOO reduces food consumption primarily through its impact on the gastrointestinal tract, making it a recommended adjunct for weight loss. Conversely, the intake of PO limits food consumption in the absence of an autonomic reaction, but it is not advised due to its contribution to the development of cardiometabolic disorders.

Discovery of oxazine-linked pyrimidine as an inhibitor of breast cancer growth and metastasis by abrogating NF-κB activation.

Introduction: Nuclear factor kappa (NF-κB) plays a key role in cancer cell proliferation; thus, small molecule inhibitors of NF-κB activity can effectively inhibit breast cancer (BC) progression. We have previously reported oxazine and piperazine-linked pyrimidines as novel anti-cancer agents that can suppress NF-κB activation in BC cells. Moreover, the TRX-01 compound, an oxazine-linked pyrimidine, inhibited MCF-7 cells at a concentration of 9.17 µM in the Alamar Blue assay. Methods: This work involved the analysis of frontier molecular orbitals, HOMO-LUMO interactions, and molecular electrostatic potential for the TRX-01 structure. Additionally, the TRX-01 compound was studied for cytotoxicity, and migration as well as invasion assays were performed on BC cells. Results: Finally, TRX-01 blocked the translocation of NF-κB from the cytoplasm to the nucleus in MCF-7 cells and reduced NF-κB and IκBα levels in a dose-dependent manner. It also suppressed migratory and invasive properties of BC cells. Conclusion: Overall, the data indicates that TRX-01 can function as a novel blocker of BC growth and metastasis by targeting NF-κB activation.

Small molecule communication of Legionella: the ins and outs of autoinducer and nitric oxide signaling.

SUMMARYLegionella pneumophila is a Gram-negative environmental bacterium, which survives in planktonic form, colonizes biofilms, and infects protozoa. Upon inhalation of Legionella-contaminated aerosols, the opportunistic pathogen replicates within and destroys alveolar macrophages, thereby causing a severe pneumonia termed Legionnaires' disease. Gram-negative bacteria employ low molecular weight organic compounds as well as the inorganic gas nitric oxide (NO) for cell-cell communication. L. pneumophila produces, secretes, and detects the α-hydroxyketone compound Legionella autoinducer-1 (LAI-1, 3-hydroxypentadecane-4-one). LAI-1 is secreted by L. pneumophila in outer membrane vesicles and not only promotes communication among bacteria but also triggers responses from eukaryotic cells. L. pneumophila detects NO through three different receptors, and signaling through the volatile molecule translates into fluctuations of the intracellular second messenger cyclic-di-guanylate monophosphate. The LAI-1 and NO signaling pathways are linked via the pleiotropic transcription factor LvbR. In this review, we summarize current knowledge about inter-bacterial and inter-kingdom signaling through LAI-1 and NO by Legionella species.

Orthologs of Plasmodium ICM1 are dispensable for Ca2+ mobilization in Toxoplasma gondii.

Apicomplexan parasites mobilize ionic calcium (Ca2+) from intracellular stores to promote microneme secretion and facilitate motile processes including gliding motility, invasion, and egress. Recently, a multipass transmembrane protein, ICM1, was found to be important for calcium mobilization in Plasmodium falciparum and P. berghei. Comparative genomics and phylogenetics have revealed putative ICM orthologs in Toxoplasma gondii and other apicomplexans. T. gondii possesses two ICM-like proteins, which we have named TgICM1-L (TGGT1_305470) and TgICM2-L (TGGT1_309910). TgICM1-L and TgICM2-L localized to undefined puncta within the parasite cytosol. TgICM1-L and TgICM2-L are individually dispensable in tachyzoites, suggesting a potential compensatory relationship between the two proteins may exist. Surprisingly, mutants lacking both TgICM1-L and TgICM2-L are fully viable, exhibiting no obvious defects in growth, microneme secretion, invasion, or egress. Furthermore, loss of TgICM1-L, TgICM2-L, or both does not impair the parasite's ability to mobilize Ca2+. These findings suggest that additional proteins may participate in Ca2+ mobilization or import in Apicomplexa, reducing the dependence on ICM-like proteins in T. gondii. Collectively, these results highlight similar yet distinct mechanisms of Ca2+ mobilization between T. gondii and Plasmodium.IMPORTANCECa2+ signaling plays a crucial role in governing apicomplexan motility; yet, the mechanisms underlying Ca2+ mobilization from intracellular stores in these parasites remain unclear. In Plasmodium, the necessity of ICM1 for Ca2+ mobilization raises the question of whether this mechanism is conserved in other apicomplexans. Investigation into the orthologs of Plasmodium ICM1 in T. gondii revealed a differing requirement for ICM proteins between the two parasites. This study suggests that T. gondii employs ICM-independent mechanisms to regulate Ca2+ homeostasis and mobilization. Proteins involved in Ca2+ signaling in apicomplexans represent promising targets for therapeutic development.