Sperm Flagellar 1 Binds Actin in Intestinal Epithelial Cells and Contributes to Formation of Filopodia and Lamellipodia

Deoxynivalenol Induces Intestinal Epithelial Barrier Damage through RhoA/ROCK Pathway-Mediated Apoptosis and F-Actin-Associated Tight Junction Disruption

Deoxynivalenol (DON) poses a serious global food safety risk due to its high toxicity and contamination rate. It disrupts the intestinal epithelial barrier, allowing exogenous toxins to enter the circulation and resulting in sepsis and systemic toxicity. In this research, 32 male Kunming mice and Porcine Small Intestinal Epithelial (IPEC-J2) cells were treated with DON at 0-4.8 mg/kg (7 d) and 0-12 μM (24 h), respectively. Histopathological results revealed that DON disrupted the intestinal epithelial barrier, causing apoptosis and tight junction (TJ) injury. Immunofluorescence and protein expression results showed that DON-induced p53-dependent mitochondrial pathway apoptosis and fibrillar actin (F-actin)-associated TJ injury and that the RhoA/ROCK pathway were activated in mice jejunal tissue and IPEC-J2 cells. Pretreatment with RhoA or ROCK inhibitors (Rosin or Y-27632) maintained DON-induced apoptosis and F-actin-associated TJ injury in IPEC-J2 cells. Thus, DON induces damage to the intestinal epithelial barrier through the RhoA/ROCK pathway-mediated apoptosis and F-actin-associated TJ disruption.

Interaction of LARP4 to filamin A mechanosensing domain regulates cell migrations

Filamin A (FLNA) is an actin cross-linking protein that mediates mechanotransduction. Force-dependent conformational changes of FLNA molecule expose cryptic binding site of FLNA, allowing interaction with partners such as integrin, smoothelin, and fimbacin. Here, we identified La-related protein 4 (LARP4) as a new FLNA mechanobinding partner. LARP4 specifically interacts with the cleft formed by C and D strands of immunoglobulin-like repeat 21 (R21) which is blocked by A strand of R20 without force. We validated the interaction between LARP4 and FLNA R21 both in vivo and in vitro. We also determined the critical amino acid that is responsible for the interaction and generated the non-FLNA-binding mutant LARP4 (F277A in human: F273A in mouse Larp4) that disrupts the interaction. Fluorescence recovery after photobleaching (FRAP) of GFP-labeled LARP4 in living cells demonstrated that mutant LARP4 diffuses faster than WT LARP4. Proximity ligation assay (PLA) also confirmed their interaction and disruption of actin polymerization diminishes the interaction. Data mining of RNAseq analysis of LARP4 knockdown (KD) HEK293T cells suggested that LARP4 is involved in morphogenesis and cell motility. Consistent with this prediction, we found that KD of LARP4 increases cell migration speed and expression of the F277A mutant LARP4 in LARP4-KD cells also leads to a higher cell migration speed compared to WT LARP4. These results demonstrated that the LARP4 interaction with FLNA regulates cell migration.

Spef1/CLAMP binds microtubules and actin-based structures and regulates cell migration and epithelia cell polarity

During migration, cells invade, repair, and create barriers leading to the formation of new cellular contacts in target tissues. Cell migration requires many proteins that collectively form the cytoskeleton. The main cytoskeletal elements are actin filaments, microtubules (MTs), and intermediate filaments. These structures work in concert with a large number of accessory proteins that contribute in a variety of ways to regulate filament assembly and turnover, to alter the configuration or arrangement of filaments by bundling or crosslinking, to link the cytoskeleton to other structures in the cell, such as membranes and junctions, and to transport cargo along the filaments. Sperm flagella protein-1 (Spef1), also designated calponin homology and microtubules-associated protein (CLAMP), is a multifunctional protein that interacts with cytoskeletal structures, including MTs, actin filaments, and focal adhesions in epithelia. In this review, we outline Spef1/CLAMP structure and expression in several cellular models. The function of Spef1/CLAMP in flagellar and ciliary motility, MT-binding and stability, regulation of planar cell polarity, and potential contribution to the maintenance of actin-based structures, such as lamellipodia and filopodia during cell migration, are also discussed.

Exposure to desflurane anesthesia confers colorectal cancer cells metastatic capacity through deregulation of miR-34a/LOXL3

Due to high potency and low toxicity, desflurane has been widely used during surgery. Recent evidence that the use of desflurane was associated with colorectal cancer (CRC) tumor metastasis and poor prognosis raising concerns about the safety of desflurane. However, the mechanism was uncovered. CRC cells were exposed to desflurane, the changes in morphology and epithelial-mesenchymal transition (EMT)-related genes were evaluated. Transwell assay was used to study the migration and invasion effect. Xenograft was performed to study the tumor formation ability of desflurane-treated cells in vivo. Dual-luciferase reporter assay was conducted to verify the target of microRNA (miR)-34a. Knockdown or overexpression of LOXL3 was used to investigate the mechanism of desflurane-induced EMT. The association of LOXL3 with CRC molecular subtypes and clinical relevance was studied by analysis of public datasets. Exposure to desflurane induced EMT, migration, and invasion in CRC cells. Mice injected with desflurane-treated cells formed more tumors in the lungs. Downregulation of miR-34a and upregulation of LOXL3 were required for desflurane-induced EMT in CRC cells. LOXL3 was a direct target of miR-34a. Overexpression of LOXL3 rescued miR-34a-repressed EMT after exposure to desflurane. Elevated expression of LOXL3 was enriched in CMS4 and CRIS-B subtypes. Patients with high expression of LOXL3 showed more lymph node metastasis, as well as poor survival. Desflurane induced EMT and metastasis in CRC through deregulation of miR-34a/LOXL3 axis. Clinical miR-34a mimic or inhibitor targeting LOXL3 might have a potential protective role when patients with CRC anesthetized by desflurane.

Yes-associated protein upregulates filopodia formation to promote alveolar epithelial-cell phagocytosis

Cells engulf particles larger than 0.5 μm in diameter by phagocytosis, which is driven by cytoskeletal rearrangements. Phagocytosis by alveolar epithelial cells (AECs) helps to maintain the alveolar homeostasis. Yes-associated protein (YAP), a transcriptional coactivator of the Hippo pathway, affects proliferation, differentiation, and cytoskeletal rearrangement of AECs, but it is not clear whether YAP regulates phagocytosis. In this study, interference with YAP expression inhibited phagocytosis in MLE-12 cells and in primary cultures of AEC. Filopodia formation promoted phagocytosis in AECs, and YAP enhanced filopodia formation in AECs. Blocking PI3K signaling resulted in reduced YAP protein expression and inhibition of phagocytosis. The results indicate that YAP expression was regulated by PI3K signaling and promoted phagocytosis in AECs by upregulating filopodia formation.