Girdin is phosphorylated on tyrosine 1798 when associated with structures required for migration

Girdin deficiency causes developmental and epileptic encephalopathy with hippocampal sclerosis and interneuronopathy

OBJECTIVE

Loss-of-function mutations in the GIRDIN/CCDC88A gene cause developmental epileptic encephalopathy (DEE) in humans. However, its pathogenesis is largely unknown. Global knockout mice of the corresponding orthologous gene (gKOs) have a preweaning lethal phenotype with growth failure, preventing longitudinal analysis. We aimed to overcome this lethality and elucidate DEE pathogenesis.

METHODS

We developed a novel lifelong feeding regimen (NLFR), which consists of providing mash food from postnatal day 14 (P14) until weaning (P28), followed by agar-bound food exclusively after weaning. Videography, electroencephalography (EEG), and histological analyses were performed. Conditional Girdin/Ccdc88a knockout mice (cKOs) of variable lineages (Nestin, Emx1, or Nkx2-1) were generated to identify the region responsible for epilepsy.

RESULTS

Under the NLFR, gKOs survived beyond 1 year and displayed fully penetrant, robust epileptic phenotypes, including early-onset (P22.3 in average) generalized tonic-clonic seizures (GTCSs) (averaging eight per day), which were completely synchronized with fast rhythms on EEG, frequent interictal electroencephalographic spikes (averaging 430 per hour), and progressive deformation of visceral organs. In addition, gKOs had absence seizures, which were not always time-locked to frequent spike waves on EEG. The frequent GTCSs and interictal spikes in gKOs were suppressed by known antiepileptic drugs. Histologically, bilateral hippocampi in gKOs exhibited congenital cornu-ammonis splitting, granule cell dispersion, and astrogliosis. Furthermore, analysis of conditional knockouts using multiple Cre-deleters identified a defect in the delivery of interneuron precursors from the medial ganglionic eminence into the hippocampal primordium during embryogenesis as a major cause of epileptogenesis.

SIGNIFICANCE

These findings give rise to a new approach of lifelong caregiving to overcome the problem of preweaning lethality in animal models. We propose a useful model for studying DEE with hippocampal sclerosis and interneuronopathy. gKOs with NLFR combine the contradictory properties of robust epileptic phenotypes and long-term survivability, which can be used to investigate spontaneous epileptic wave propagation and therapeutic intervention in hippocampal sclerosis.

Girdin regulates both migration and angiogenesis in pancreatic cancer cell lines

Girdin, an actin‑binding protein, is reportedly involved in the invasion and angiogenesis of various cancers. It has been suggested that the flavonoid Scutellarin (SCU) inhibits Girdin signaling. In the present study, the function and therapeutic applications of Girdin in pancreatic cancer (PaCa) were investigated. Immunohistochemical staining of Girdin in resected PaCa specimens from the Department of Gastroenterological Surgery, Nagoya City University Graduate School of Medical Science showed that high Girdin expression was associated with poor overall survival and relapse‑free survival, as well as with T factor, indicating invasion into the surrounding tissues. On the other hand, Girdin was highly expressed in almost all PaCa cell lines, and the migration ability of Girdin‑knockdown cell lines was decreased even under epidermal growth factor (EGF) stimulation. In addition, SCU suppressed PaCa cell migration by inhibiting the phosphorylation of Girdin. The expression and production of vascular endothelial growth factor A (VEGF‑A) was significantly decreased in Girdin‑knockdown cell lines. Furthermore, in Matrigel tube formation assays performed using culture supernatant, the lumen‑forming ability of vascular endothelial cells was also decreased in Girdin‑knockdown cell lines. However, SCU treatment did not significantly alter the expression or production of VEGF‑A. These results suggested that Girdin is involved in EGF signaling‑mediated migration of PaCa cells, that SCU inhibits PaCa invasion by suppressing Girdin activity, and that Girdin is also involved in angiogenesis via an activation pathway different from the action site of SCU. Girdin may be a prognostic biomarker, and the development of a novel molecular‑targeted drugs for Girdin may improve the prognosis of PaCa in the future.

Knockdown of Girdin Induced Apoptosis of Glioblastoma Cells via the Mitochondrion Signaling Pathway

Glioblastoma is the most common primary brain tumor with poor survival rate and without effective treatment strategy. However, the influence of Girdin on human glioblastoma and the underlying molecular mechanisms have yet to be uncovered. We mainly investigated the role of Girdin in glioblastoma cells apoptosis. First, we examined Girdin expression in 90 glioma patients by using immunohistochemistry (IHC) and analyzed its association with patients' prognosis. The results showed that the expression of Girdin was positively associated with the histological grade of glioma, and glioma patients with high Girdin expression had a poor prognosis. Next, proliferation assay, Colony formation assay and Cell Counting Kit-8 (CCK-8) results showed that knockdown of Girdin suppressed proliferation and reduced cell survival rate. Flow cytometry and DAPI staining results showed that knockdown of Girdin induced apoptosis in LN229 cells. Western blot results suggested that reduction of Gridin increased the level of Cytochrome C (Cyt-C) and Bad while decreased the expression of Bcl-2 and p-AKT. Moreover, subcutaneous mouse xenograft model was used to validate the role of Girdin in glioblastoma apoptosis. Consistently, in vivo assays showed that knockdown of Girdin inhibited the growth of the grafted tumor and increased the level of Cyt-C and Bad. These findings demonstrated that knockdown of Girdin may induce Bad expression and reduce Bcl-2 expression by inhibiting the activation of AKT, leading to the release of Cyt-C from mitochondria, thereby promoting glioblastoma cells apoptosis.

Distribution of duodenal tuft cells is altered in pediatric patients with acute and chronic enteropathy

Clinical interest into the function of tuft cells in human intestine has increased in recent years. However, no quantitative study has examined intestinal tuft cells in pathological specimens from patients. This study quantified tuft cell density by using a recently identified marker, specific for tyrosine phosphorylation (pY1798) of girdin (also known as CCDC88A or GIV) in the duodenum of pediatric patients. Deidentified sections with pathological diagnosis of acute duodenitis, ulcer, or celiac disease, and age-matched normal control were analyzed under double-blind conditions. Immunostaining for pY1798-girdin demonstrated the distinct shape of tuft cells with and filopodia-like basolateral membrane structure and a small apical area, which densely expressed gamma-actin. As compared to normal tissues, the specimens diagnosed as celiac disease and duodenal ulcer had significantly fewer tuft cell numbers. In contrast, acute duodenitis showed varied population of tuft cells. The mucosa with severe inflammation showed lower tuft cell numbers than the specimens with none to mild inflammation. These results suggest that loss of tuft cells may be involved in prolonged inflammation in the duodenal mucosa and disrupted mucosal integrity. pY1798-girdin and gamma-actin are useful markers for investigating the distribution and morphologies of human intestinal tuft cells under healthy and pathological conditions.

In Vivo Electroporation and Time-Lapse Imaging of the Rostral Migratory Stream in Developing Rodent Brain

Interneurons in the olfactory bulb are generated from neuronal precursor cells migrating from the anterior subventricular zone (SVZa) throughout the embryonic and postnatal life of mammals. This article describes basic methods for in vivo electroporation to label SVZa cells of both embryonic and postnatal rats. In addition, it describes three methods for tracing SVZa progenitors and following their migration pathway and differentiation, including immunohistochemistry, time-lapse live imaging in slice culture, and time-lapse imaging following transplantation in slice culture. These methods may be applied to all strains of rats and mice, including reporter mice. They may also be combined with methods such as BrdU labeling, tamoxifen injection, and electrophysiology, allowing one to observe proliferation or control gene expression at specific times and for specific neuronal functions. With time-lapse live imaging, details of labeled cells can be studied, including morphology, motility pattern, differentiation, and crosstalk between cells. © 2019 by John Wiley & Sons, Inc.

Single-Cell Imaging of Metastatic Potential of Cancer Cells

Molecular imaging of metastatic “potential” is an unvanquished challenge. To engineer biosensors that can detect and measure the metastatic “potential” of single living cancer cells, we carried out a comprehensive analysis of the pan-cancer phosphoproteome to search for actin remodelers required for cell migration, which are enriched in cancers but excluded in normal cells. Only one phosphoprotein emerged, tyr-phosphorylated CCDC88A (GIV/Girdin), a bona fide metastasis-related protein across a variety of solid tumors. We designed multi-modular biosensors that are partly derived from GIV, and because GIV integrates prometastatic signaling by multiple oncogenic receptors, we named them “‘integrators of metastatic potential (IMP).” IMPs captured the heterogeneity of metastatic potential within primary lung and breast tumors at steady state, detected those few cells that have acquired the highest metastatic potential, and tracked their enrichment during metastasis. These findings provide proof of concept that IMPs can measure the diversity and plasticity of metastatic potential of tumor cells in a sensitive and unbiased way.

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Phosphoproteomes of cancers predicted a putative metastasis-specific phosphoevent

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FRET-based biosensor designed to assess this phosphoevent in living cells

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Biosensor tracks the diversity and plasticity of metastatic potential of cancer cells

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These sensors could direct drug efficacy testing against the most sinister cancer cells

Visualization of Rostral Migratory Stream in the Developing Rat Brain by In Vivo Electroporation

Interneurons in the olfactory bulb (OB) are generated from neuronal precursor cells migrating from anterior subventricular zone (SVZa) not only in the developing embryo but also throughout the postnatal life of mammals. In the present study, we established an in vivo electroporation assay to label SVZa cells of rat both at embryonic and postnatal ages, and traced SVZa progenitors and followed their migration pathway and differentiation. We found that labeled cells displayed high motility. Interestingly, the postnatal cells migrated faster than the embryonic cells after applying this assay at different ages of brain development. Furthermore, based on brain slice culture and time-lapse imaging, we analyzed the detail migratory properties of these labeled precursor neurons. Finally, tissue transplantation experiments revealed that cells already migrated in subependymal zone of OB were transplanted back into rostral migratory stream (RMS), and these cells could still migrate out tangentially along RMS to OB. Taken together, these findings provide an in vivo labeling assay to follow and trace migrating cells in the RMS, their maturation and integration into OB neuron network, and unrecognized phenomena that postnatal SVZa progenitor cells with higher motility than embryonic cells, and their migration was affected by extrinsic environments.

Use of Anti-phospho-girdin Antibodies to Visualize Intestinal Tuft Cells in Free-Floating Mouse Jejunum Cryosections

The actin binding protein girdin is a cytosolic protein that is required for actin remodeling to trigger cell migration in various tissues. Girdin is phosphorylated by both receptor and non-receptor tyrosine kinases at tyrosine 1798. Omori et al. developed site- and phosphorylation status-specific antibodies against human girdin at tyrosine-1798 (pY1798), which specifically bind to phosphorylated tyrosine-1798, but not to unphosphorylated tyrosine-1798. pY1798 antibodies have been used to specifically label tuft cells (TCs) that are present in mammalian gastrointestinal tissues, but the function of these cells is unclear. This protocol allows the robust visualization of TCs in the jejunum using pY1798 antibodies and immunofluorescence. To ensure successful and simple TC visualization, this protocol includes two histological techniques: production of free-floating cryosections from gelatin-filled jejunum tissue, and low-temperature antigen retrieval at 50 °C for 3 h. Filling the jejunum with gelatin maintains the shape of free-floating sections throughout the staining procedure, whereas low-temperature antigen retrieval ensures robust signals from TCs. Successful use of this protocol results in pY1798 staining of TCs distributed from villus tip to crypt. Stained TCs have a spool-shaped soma and fluorescent signals condense at the lumenal tip, which corresponds to the protruding 'tuft.' Phalloidin staining colocalized with pY1798-positive TCs at the thickened brush border, and corresponds to a rootlet mass extending from the TC tuft. This protocol could be used to examine TCs in human biopsy samples collected with gastrointestinal endoscopes. Furthermore, TCs were recently reported to accumulate following parasite infection in mice, suggesting that this protocol could have applications for diagnosis of parasite infections in the human gut.

Girdin protein: A potential metastasis predictor associated with prognosis in lung cancer

The present study explored the relationship between Girdin protein expression and the survival rate of patients with lung carcinoma. A total of 334 lung cancer specimens, 20 benign lung disease tissue sections and 24 fresh tissues from patients with lung carcinoma were analyzed by immunohistochemistry and western blotting. Girdin protein was expressed in 130/334 (38.93%) of the cases examined. Girdin protein expression was correlated with tumor/node/metastasis stage (P<0.001), lymph node metastasis (P=0.001), distant metastasis (P<0.001) and specimen sites (P=0.034). Girdin expression was also correlated with signal transducer and activator of transcription 3 (STAT3) expression (P<0.001). Patients with high Girdin and STAT3 expression had a significantly poorer prognosis compared with those with low/high, high/low or low/low expression (P<0.001). In summary, Girdin may be a prognostic marker of lung cancer and serve as a biomarker for metastasis.

Tyrosine Phosphorylation of an Actin-Binding Protein Girdin Specifically Marks Tuft Cells in Human and Mouse Gut

Tuft cells (TCs) are minor components of gastrointestinal epithelia, characterized by apical tufts and spool-shaped somas. The lack of reliable TC-markers has hindered the elucidation of its role. We developed site-specific and phosphorylation-status-specific antibodies against Girdin at tyrosine-1798 (pY1798) and found pY1798 immunostaining of mouse jejunum clearly depicted epithelial cells closely resembling TCs. This study aimed to validate pY1798 as a TC-marker. Double-fluorescence staining of intestines was performed with pY1798 and known TC-markers, for example, hematopoietic-prostaglandin-D-synthase (HPGDS), or doublecortin-like kinase 1 (DCLK1). Odds ratios (ORs) were calculated from cell counts to determine whether two markers were attracting (OR<1) or repelling (OR>1). In consequence, pY1798 signals strongly attracted those of known TC-markers. ORs for HPGDS in mouse stomach, small intestine, and colon were 0 for all, and 0.08 for DCLK1 in human small intestine. pY1798-positive cells in jejunum were distinct from other minor epithelial cells, including goblet, Paneth, and neuroendocrine cells. Thus, pY1798 was validated as a TC-marker. Interestingly, apoptosis inducers significantly increased relative TC frequencies despite the absence of proliferation at baseline. In conclusion, pY1798 is a novel TC-marker. Selective tyrosine phosphorylation and possible resistance to apoptosis inducers implied the activation of certain kinase(s) in TCs, which may become a clue to elucidate the enigmatic roles of TCs. .

Collective invasion of cancer: Perspectives from pathology and development

Clinical pathologists have long been aware that in many types of human malignant tumors, the cells are often connected and form groups of various sizes or "nests". In this way, they achieve "collective invasion" into the surrounding stroma, rather than spreading out individually. Such collective behavior is also a common feature of migration during embryonic and postnatal developmental stages, suggesting there are advantages gained by collective cell migration in the organisms. Recent studies have revealed the mechanisms underlying the collective invasion of cancer cells. These mechanisms differ from those observed in the migration of single cells in culture, including reliance on the epithelial-mesenchymal transition program. Whereas intercellular adhesion appears to be coordinated, cancer cell groups can be heterogenous, including cells that are leaders and those that are followers. There is also interaction with the tumor microenvironment that is a prerequisite for collective invasion of cancer. In this review, we describe recently emerging mechanisms underlying the collective migration of cells, with a particular focus in our studies on the actin-binding protein Girdin/GIV and the transcriptional regulator tripartite motif containing 27. These studies provide new perspectives on the mechanistic analogy between cancer and development.

GIV/Girdin (Gα-interacting, Vesicle-associated Protein/Girdin) Creates a Positive Feedback Loop That Potentiates Outside-in Integrin Signaling in Cancer Cells

Activation of the tyrosine kinase focal adhesion kinase (FAK) upon cell stimulation by the extracellular matrix initiates integrin outside-in signaling. FAK is directly recruited to active integrins, which enhances its kinase activity and triggers downstream signaling like activation of PI3K. We recently described that Gα-interacting, vesicle-associated protein (GIV), a protein up-regulated in metastatic cancers, is also required for outside-in integrin signaling. More specifically, we found that GIV is a non-receptor guanine nucleotide exchange factor that activates trimeric G proteins in response to integrin stimulation to enhance PI3K signaling and tumor cell migration. In contrast, previous reports have established that GIV is involved in phosphotyrosine (Tyr(P))-based signaling in response to growth factor stimulation;i.e.GIV phosphorylation at Tyr-1764 and Tyr-1798 recruits and activates PI3K. Here we show that phosphorylation of GIV at Tyr-1764/Tyr-1798 is also required to enhance PI3K-Akt signaling and tumor cell migration in response to integrin stimulation, indicating that GIV functions in Tyr(P)-dependent integrin signaling. Unexpectedly, we found that activation of FAK, an upstream component of the integrin Tyr(P) signaling cascade, was diminished in GIV-depleted cells, suggesting that GIV is required to establish a positive feedback loop that enhances integrin-FAK signaling. Mechanistically, we demonstrate that this feedback activation of FAK depends on both guanine nucleotide exchange factor and Tyr(P) GIV signaling as well as on their convergence point, PI3K. Taken together, our results provide novel mechanistic insights into how GIV promotes proinvasive cancer cell behavior by working as a signal-amplifying platform at the crossroads of trimeric G protein and Tyr(P) signaling.