Explore the vast range of titles available.

Calpains, calcium-dependent cytosolic cysteine proteases, perform controlled proteolysis of their substrates for various cellular and physiological activities. In different cancers, missense mutations accumulate in the genes coding for the calpain cleavage sites in various calpain substrates termed as the calpain cleavage-related mutations (CCRMs). However, the impact of such CCRMs on the calpain–substrate interaction is yet to be explored. This study focuses on the interaction of wild-type and mutant β-integrins with calpain-1 and 2 in uterine corpus endometrial carcinoma (UCEC). A total of 48 calpain substrates with 176 CCRMs were retrieved from different datasets and shortlisted on the basis of their involvement in cancer pathways. Finally, three calpain substrates, ITGB1, ITGB3, and ITGB7, were selected to assess the structural changes due to CCRMs. These CCRMs were observed towards the C-terminal of the cytoplasmic domain within the calpain cleavage site. The wild-type and mutant proteins were docked with calpain-1 and 2, followed by molecular simulation. The interaction between mutant substrates and calpains showcased variations compared to their respective wild-type counterparts. This may be attributed to mutations in the calpain cleavage sites, highlighting the importance of the cytoplasmic domain of β-integrins in the interactions with calpains and subsequent cellular signaling. Highlights: 1. Calpain cleavage-related mutations (CCRMs) can alter cellular signaling. 2. CCRMs impact the structure of C-domains of human integrin-β subunits. 3. Altered structure influences the cleavability of human integrin-β subunits by human calpains. 4. Altered cleavability impacts the cell signaling mediated through calpain–integrin-β axis. 5. Presence of CCRMS may influence the progression of uterine corpus endometrial carcinoma (UCEC).

Calpain‐1, a calcium‐activated neutral cysteine proteases, has been reported to be involved in the formation of pulmonary hypertension. HIF‐1α, an oxygen‐sensitive transcription factor, has been reported to activate genes involved in cell proliferation and extracellular matrix recombination. This study was designed to investigate the effect of calpain‐1 in hypoxic pulmonary hypertension (HPH) and to explore whether there is a relationship between calpain‐1 and HIF‐1α in this disease. In the hypoxia‐induced model of HPH, we found that hypoxia resulted in increased right ventricular systolic pressure, right ventricular hypertrophy, pulmonary vascular remodelling and collagen deposition in lung tissues of mice. The levels of calpain‐1 and HIF‐1α were up‐regulated in the lung tissues of hypoxia‐treated mice and pulmonary arterial smooth muscle cells (PASMCs). Knock‐out of calpain‐1 restrained haemodynamic and histological changes induced by chronic hypoxia in mice, and inhibition of calpain‐1 also repressed the abnormal proliferation and migration of PASMCs. Besides, knock‐out or inhibition of calpain‐1 suppressed hypoxia‐induced expression of HIF‐1α, VEGF, PCNA, TGF‐β1, MMP2 and collagen I in vivo and in vitro. While inhibition of HIF‐1α abolished the above effects of calpain‐1. Furthermore, we found that calpain‐1 mediates the expression of HIF‐1α through NF‐κB (P65) under hypoxia conditions. In conclusion, our results suggest that calpain‐1 plays a pivotal role in hypoxia‐induced pulmonary vascular remodelling and fibrosis through HIF‐1α, providing a better understanding of the pathogenesis of HPH.

Calpains are a family of nonlysosomal cysteine proteases, which play important roles in numerous physiological and pathological processes. Locations of them dictates the functions so that they are classified as ubiquitously expressed calpains and tissue-specific calpains. Recent studies are mainly focused on conventional calpains (calpain-1,2) in development and diseases, and increasing people pay attention to other subtypes of calpains but may not been summarized appropriately. Growing evidence suggests that calpains are also involved in immune regulation. However, seldom articles review the regulation of calpains on immune cells. The aim of this article is to review the research progress of each calpain isozyme and the effect of calpains on immune cells, especially the promotion effect of calpains on the immune response of macrophage, neutrophils, dendritic cells, mast cells, natural killed cells, and lymphocytes. These effects would hold great promise for the clinical application of calpains as a practicable therapeutic option in the treatment of immune related diseases.

It is considered a significant challenge to understand the neuronal cell death mechanisms with a suitable cure for neurodegenerative disorders in the coming years. Calpains are one of the best-considered “cysteine proteases activated” in brain disorders. Calpain is an important marker and mediator in the pathophysiology of neurodegeneration. Calpain activation being the essential neurodegenerative factor causing apoptotic machinery activation, it is crucial to develop reliable and effective approaches to prevent calpain-mediated apoptosis in degenerating neurons. It has been recently seen that the “inhibition of calpain activation” has appeared as a possible therapeutic target for managing neurodegenerative diseases. A systematic literature review of PubMed, Medline, Bentham, Scopus, and EMBASE (Elsevier) databases was conducted. The present article reviews the basic pathobiology and role of selective calpain inhibitors used in various neurodegenerative diseases as a therapeutic target. Graphical Abstract

The DEFECTIVE KERNEL 1 (DEK1) protein plays essential functions throughout plant development. DEK1 is a multidomain 240 kDa protein with yet unsolved 3D structure. To facilitate structural and functional studies of DEK1, here we investigate its calpain protease core domain (CysPc) from Physcomitrium patens . Using integrated structural modelling we propose targeted mutagenesis of CysPc to enhance its solubility during recombinant protein production. We created a pipeline to predict the topology of the CysPc domain with improved precision, providing a robust framework for further exploration. We evaluated the native and mutant structures by MD simulations, concentrating on several solubility-related parameters. Following these features, we implemented specific single, double, and triple amino acid mutagenesis to select variants with improved solubility. Our method preserves overall structural integrity while reducing aggregation-prone traits. We advocate for the utilization of optimized data driven method that can effectively traverse the extensive combinatorial space and prioritize mutation sets with the greatest potential for enhancing solubility. This framework provides a logical, data-driven approach to improving protein solubility, particularly beneficial in situations lacking high-resolution structural data.

Reperfusion after ischemia would cause massive myocardial injury, which leads to oxidative stress (OS). Calcium homeostasis imbalance plays an essential role in myocardial OS injury. Ca[sub.V]1.2 calcium channel mediates calcium influx into cardiomyocytes, and its activity is modulated by a region of calpastatin (CAST) domain L, CS[sub.L]54-64. In this study, the effect of Ahf-caltide, derived from CS[sub.L]54-64, on myocardial OS injury was investigated. Ahf-caltide decreased the levels of LDH, MDA and ROS and increased heart rate, coronary flow, cell survival and SOD activity during OS. In addition, Ahf-caltide permeated into H9c2 cells and increased Ca[sub.V]1.2, Ca[sub.V]β2 and CAST levels by inhibiting protein degradation. At different Ca[sup.2+] concentrations (25 nM, 10 μM, 1 mM), the binding of CS[sub.L] to the IQ motif in the C terminus of the Ca[sub.V]1.2 channel was increased in a H[sub.2]O[sub.2] concentration-dependent manner. CS[sub.L]54-64 was predicted to be responsible for the binding of CS[sub.L] to Ca[sub.V]1.2. In conclusion, Ahf-caltide exerted a cardioprotective effect on myocardial OS injury by stabilizing Ca[sub.V]1.2 protein expression. Our study, for the first time, proposed that restoring calcium homeostasis by targeting the Ca[sub.V]1.2 calcium channel and its regulating factor CAST could be a novel treatment for myocardial OS injury.

Limb–girdle muscular dystrophy Type 2A/R1 or calpain‐3 deficiency is the most common autosomal recessive limb–girdle muscular dystrophy. However, in recent years, autosomal dominant cases and families with calpain‐3 deficiency have been reported, and there is an emerging interest in looking for single variants in the calpain‐3 gene in mildly to moderately affected patients with limb–girdle muscular dystrophy without biallelic gene variants in CAPN3 . Here, we report four cases with creatine kinase levels above 1500 U/L, mild‐to‐moderate proximal weakness, waddling gait, and scapular winging. Two patients, a son and his father, are heterozygous for the CAPN3 variant c.304C>T; p.(Pro102Ser), which has previously been reported in patients with compound heterozygous variants in CAPN3 . The third and fourth patients were heterozygous for c.1371C>G; p.(Asn457Lys) and c.1490C>T; p.Ala497_Glu508del, respectively, neither of which has been reported before. All four patients had a near‐complete loss of calpain‐3 as determined by western blotting. While inherited autosomal dominant calpainopathy has now been firmly established, additional single cases of dominant calpainopathy are likely to emerge; some will be associated with clinical findings from parents or siblings, while others will arise from spontaneous mutations, but nevertheless with similar clinical findings of mild‐to‐moderate proximal weakness, increased level of creatine kinase, and near‐complete loss of calpain‐3 protein in affected individuals. This report expands the known number of variants causing dominant calpainopathy from 8 to 11 that appears to exclusively reside in two out of four domains that make up calpain‐3. This information could aid in determining whether a CAPN3 variant of unknown significance is pathological.

The placenta is often described as the “window to the brain” due to its crucial role in fetal neurological development. In this study, we investigated a family where the older male offspring exhibited severe neurodevelopmental and mild motor coordination disorders. His brother displayed emotional and behavioral dysregulation along with mild motor coordination disorders. The father was asymptomatic, while the mother and daughter showed mild learning disabilities. Whole exome sequencing (WES) identified a disruptive X-linked pathogenic variant, c.1088_1089del p.Asp363GlyfsTer2, within the calpain-6 (CAPN6) gene. We have submitted this variant to the ClinVar database (RCV005234146.2). The variant was found in hemizygous condition in the affected male offspring and in heterozygous condition in both the mother and daughter. As predicted, the variant undergoes nonsense-mediated mRNA decay (NMD), preventing the translation of the CAPN6 gene into a functional protein. CAPN6 is a critical gene predominantly expressed in placental and trophoblast tissues. Although its function is not well characterized, CAPN6 is also expressed in several regions of the developing brain. Recent studies have shown that genetic variants in CAPN6 significantly influence vascular endothelial growth factor (VEGF) activity, thereby affecting angiogenesis and the blood supply essential for fetal growth and development. Although CAPN6 lacks an MIM phenotype code, we hypothesize that it might be enumerated as a novel candidate gene contributing to neurodevelopmental disorders. Functional studies are imperative to elucidate the role of CAPN6 in placental function and its potential implications for neurodevelopmental processes. This work aims to inspire further research into the role of CAPN6 in placental biology and its relevance to neurodevelopmental disorders.

Spinocerebellar ataxia type 17 (SCA17) is a neurodegenerative disease caused by a polyglutamine-encoding trinucleotide repeat expansion in the gene of transcription factor TATA box-binding protein (TBP). While its underlying pathomechanism is elusive, polyglutamine-expanded TBP fragments of unknown origin mediate the mutant protein’s toxicity. Calcium-dependent calpain proteases are protagonists in neurodegenerative disorders. Here, we demonstrate that calpains cleave TBP, and emerging C-terminal fragments mislocalize to the cytoplasm. SCA17 cell and rat models exhibited calpain overactivation, leading to excessive fragmentation and depletion of neuronal proteins in vivo. Transcriptome analysis of SCA17 cells revealed synaptogenesis and calcium signaling perturbations, indicating the potential cause of elevated calpain activity. Pharmacological or genetic calpain inhibition reduced TBP cleavage and aggregation, consequently improving cell viability. Our work underlines the general significance of calpains and their activating pathways in neurodegenerative disorders and presents these proteases as novel players in the molecular pathogenesis of SCA17.

Pulmonary hypertension is a severe and progressive disease, a key feature of which is pulmonary vascular remodeling. Several growth factors, including EGF, PDGF, and TGF-β1, are involved in pulmonary vascular remodeling during pulmonary hypertension. However, increased knowledge of the downstream signaling cascades is needed if effective clinical interventions are to be developed. In this context, calpain provides an interesting candidate therapeutic target, since it is activated by EGF and PDGF and has been reported to activate TGF-β1. Thus, in this study, we examined the role of calpain in pulmonary vascular remodeling in two rodent models of pulmonary hypertension. These data showed that attenuated calpain activity in calpain-knockout mice or rats treated with a calpain inhibitor resulted in prevention of increased right ventricular systolic pressure, right ventricular hypertrophy, as well as collagen deposition and thickening of pulmonary arterioles in models of hypoxia- and monocrotaline-induced pulmonary hypertension. Additionally, inhibition of calpain in vitro blocked intracellular activation of TGF-β1, which led to attenuated Smad2/3 phosphorylation and collagen synthesis. Finally, smooth muscle cells of pulmonary arterioles from patients with pulmonary arterial hypertension showed higher levels of calpain activation and intracellular active TGF-β. Our data provide evidence that calpain mediates EGF- and PDGF-induced collagen synthesis and proliferation of pulmonary artery smooth muscle cells via an intracrine TGF-β1 pathway in pulmonary hypertension.