The long Filamin-A isoform is required for intestinal development and motility: implications for chronic intestinal pseudo-obstruction

Suppression of SRC protein kinase activity alleviates the severity of aganglionosis by impairing CAV1/FLNA expression

ObjectiveHirschsprung's disease (HSCR) is a rare congenital disorder attributed to the defects of enteric neural crest cells. We aim to identify characteristic phosphorylation proteins and preliminarily explore underlying related action mechanisms in HSCR.MethodsColon samples from HSCR patients underwent proteomic and phosphoproteomic sequencing to identify differentially expressed phosphoproteins (DEPPs) and proteins (DEPs). Interaction network construction and analysis of correlations with upstream phosphorylating kinases were employed to pinpoint core proteins. HSCR rat models were established through enema administration of Benzalkonium chloride and evaluated by measuring colon cross-sectional area, colon weight, AchE, and PGP9.5 levels. Histopathological damage was assessed via hematoxylin and eosin staining. Protein expression was analyzed using western blotting. Furthermore, the impact of SRC kinase in HSCR was investigated utilizing an SRC-specific inhibitor in HSCR rat models.ResultsA total of 5725 DEPPs were identified, with SRC kinase emerging as a key regulatory protein. In the HSCR rat model, SRC expression was elevated along with increased pCAV1 and FLNA levels. Notably, inhibition of SRC protein kinase activity by 1-(tert-butyl)-3-(4-chlorophenyl)-1H-pyrazolo[3,4-d] pyrimidin-4-amine (PP2) led to reduced colon cross-sectional area and weight, an increase in the number of colonic ganglion cells, heightened AchE levels, enhanced PGP9.5 expression, and slight enlargement of the crypt, thereby alleviating HSCR symptoms in rats. Additionally, SRC kinase inhibition following PP2 treatment decreased the expression of pCAV1 and FLNA.ConclusionsInhibition of SRC kinase activity may potentially reduce CAV1/FLNA expression, ultimately alleviating the severity of HSCR in rats.

Filamin A suppresses the expression of ribosomal protein genes by controlling the activity of an EGR1-Sp1-GCN5/PCAF pathway in human cells

Human ribosome biogenesis requires four types of rRNA molecules and almost eighty cytoplasmic ribosomal proteins (CRPs) to be assembled together. . In the previous work, we showed that cytoskeletal filamin A (FLNA) can suppress rRNA expression in human cells. Thus, we hypothesized that FLNA can modulate the expression of CRPs because human cells have to coordinate cellular ribosome biogenesis. Here, we show that the absence of FLNA enhances the expression of most CRP genes assayed in the work, whereas the presence of FLNA dampens the expression of these CRP genes in several transformed cell types. The analysis of RNA-seq data revealed that FLNA silencing activated the expression of almost all CRPs and many mitochondrial RP genes in SaOS2 cells. These results indicate that FLNA acts as a negative regulator in CRP expression in human cells. Mechanistically, FLNA inhibits the expression of GCN5 and PCAF, which consequently impedes the occupancies of GCN5, PCAF, andH3K9ac at CRP gene loci. Both GCN5 and PCAF participates in the regulation of CRP expression either mediated by FLNA or independently. We show that FLNA silencing activates Sp1 expression and the activation of Sp1 stimulates the expression of Gcn5 and Pcaf genes. Further analysis revealed that EGR1 can bind the Sp1 gene promoter and activate Sp1 transcription. Collectively, this study revealed an EGR1-Sp1-GCN5/PCAF pathway by which FLNA modulates the expression of CRP genes. These findings shed light on how human cells coordinate the expression of CRP genes during ribosomal biogenesis.

Chronic intestinal pseudo-obstruction in adults: A practical guide to identify patient subgroups that are suitable for more specific treatments

Chronic intestinal pseudo-obstruction is a rare and heterogeneous syndrome characterized by recurrent symptoms of intestinal obstruction with radiological features of dilated small or large intestine with air/fluid levels in the absence of any mechanical occlusive lesion. Several diseases may be associated with chronic intestinal pseudo-obstruction and in these cases, the prognosis and treatment are related to the underlying disease. Also, in its "primary or idiopathic" form, two subgroups of patients should be determined as they require a more specific therapeutic approach: patients whose chronic intestinal pseudo-obstruction is due to sporadic autoimmune/inflammatory mechanisms and patients whose neuromuscular changes are genetically determined. In a context of a widely heterogeneous adult population presenting chronic intestinal pseudo-obstruction, this review aims to summarize a practical diagnostic workup for identifying definite subgroups of patients who might benefit from more specific treatments, based on the etiology of their underlying condition.

Traces of Canine Inflammatory Bowel Disease Reflected by Intestinal Organoids

Inflammatory bowel disease (IBD) is a chronic inflammatory condition that affects humans and several domestic animal species, including cats and dogs. In this study, we have analyzed duodenal organoids derived from canine IBD patients using quantitative proteomics. Our objective was to investigate whether these organoids show phenotypic traits of the disease compared with control organoids obtained from healthy donors. To this aim, IBD and control organoids were subjected to quantitative proteomics analysis via liquid chromatography-mass spectrometry. The obtained data revealed notable differences between the two groups. The IBD organoids exhibited several alterations at the levels of multiple proteins that are consistent with some known IBD alterations. The observed phenotype in the IBD organoids to some degree mirrors the corresponding intestinal condition, rendering them a compelling approach for investigating the disease and advancing drug exploration. Additionally, our study revealed similarities to some human IBD biomarkers, further emphasizing the translational and comparative value of dogs for future investigations related to the causes and treatment of IBD. Relevant proteins such as CALU, FLNA, MSN and HMGA2, which are related to intestinal diseases, were all upregulated in the IBD duodenal organoids. At the same time, other proteins such as intestinal keratins and the mucosal immunity PIGR were depleted in these IBD organoids. Based on these findings, we propose that these organoids could serve as a valuable tool for evaluating the efficacy of therapeutic interventions against canine IBD.

Evaluating the molecular and genetic mechanisms underlying gut motility disorders

INTRODUCTION

Gastrointestinal (GI) motility disorders comprise a wide range of different diseases affecting the structural or functional integrity of the GI neuromusculature. Their clinical presentation and burden of disease depends on the predominant location and extent of gut involvement as well as the component of the gut neuromusculature affected.

AREAS COVERED

A comprehensive literature review was conducted using the PubMed and Medline databases to identify articles related to GI motility and functional disorders, published between 2016 and 2023. In this article, we highlight the current knowledge of molecular and genetic mechanisms underlying GI dysmotility, including disorders of gut-brain interaction, which involve both GI motor and sensory disturbance.

EXPERT OPINION

Although the pathophysiology and molecular mechanisms underlying many such disorders remain unclear, recent advances in the assessment of intestinal tissue samples, genetic testing with the application of 'omics' technologies and the use of animal models will provide better insights into disease pathogenesis as well as opportunities to improve therapy.

Bioinformatic analysis of smoothelin family members supports tissue-specific functions of unique C-terminal calponin homology domains

Smoothelins are cytoskeletal proteins with a single C-terminal calponin homology domain type 2 (CHD2). Little is known about the significance of variation in SMTN CHD2 domains, addressed here through analysis of public databases. A conserved 152 nt penultimate constitutive exon present in all SMTNs encodes helices II-IV of CHD2 with high identity (nt/aa 63/65%). Variable CHD2s of SMTN (helices IV-VI) are generated by alternative splicing of 165 nt exon E20. E20 and the CHD2 it encodes have high homology with the terminal constitutive exon of SMTNL1 (E8; nt/aa 72/75% identity). Unique to these CHD2 variants are a conserved extended nine amino acid C-terminal tail containing KTKK ubiquitination motifs. When E20 of SMTN is skipped (SMTN E20-), constitutive terminal E21 codes for helices IV-VI of CHD2. SMTN E21 has high identity with the terminal exon of SMTNL2 (E8; nt/aa 75/81% identity of aligned sequences) except for coding for a unique extended C-terminus (24 nt; 8aa) conserved only in mammals. SMTN isoform expression is tissue-specific: SMTNE20- and SMTNE20+ are highly expressed in SMC and non-muscle cells, respectively, while SMTNL1 + 2 are highly expressed in skeletal muscle cells. Tissue-specific expression of SMTN CHD2s with unique helices IV-VI suggest tissue-specific functions that require further study.

The IgSF Cell Adhesion Protein CLMP and Congenital Short Bowel Syndrome (CSBS)

The immunoglobulin-like cell adhesion molecule CLMP is a member of the CAR family of cell adhesion proteins and is implicated in human congenital short-bowel syndrome (CSBS). CSBS is a rare but very severe disease for which no cure is currently available. In this review, we compare data from human CSBS patients and a mouse knockout model. These data indicate that CSBS is characterized by a defect in intestinal elongation during embryonic development and impaired peristalsis. The latter is driven by uncoordinated calcium signaling via gap junctions, which is linked to a reduction in connexin43 and 45 levels in the circumferential smooth muscle layer of the intestine. Furthermore, we discuss how mutations in the CLMP gene affect other organs and tissues, including the ureter. Here, the absence of CLMP produces a severe bilateral hydronephrosis-also caused by a reduced level of connexin43 and associated uncoordinated calcium signaling via gap junctions.