Biology subjects

Rahimi, N.

Publications and source records attributed to Rahimi, N..

5 recordsLinked to original sources

bioRxiv2021

NEDD4 Regulates Ubiquitination and Stability of the Cell adhesion Molecule IGPR-1 via Lysosomal Pathway

The cell adhesion molecule immunoglobulin and proline-rich receptor-1 (IGPR-1) regulates various critical cellular processes including, cell-cell adhesion, mechanosensing and autophagy. However, the molecular mechanisms governing IGPR-1 cell surface expression levels remains unknown. In the present study, we used an in vitro ubiquitination assay and identified ubiquitin E3 ligase NEDD4 and the ubiquitin conjugating enzyme UbcH6 involved in the ubiquitination of IGPR-1. In vitro GST-pulldown and in vivo co-immunoprecipitation assays demonstrated that NEDD4 binds to IGPR-1. Over-expression of wild-type NEDD4 downregulated IGPR-1 and deletion of WW domains (1-4) of NEDD4 revoked its effects on IGPR-1. Similarly, knockdown of NEDD4 increased IGPR-1 levels in A375 melanoma cells. Furthermore, deletion of 57 amino acids encompassing polyproline rich (PPR) motif on the C-terminus of IGPR-1 nullified the binding of NEDD4 with IGPR-1. Moreover, we demonstrate that NEDD4 promotes K48- and K63-dependent polyubiquitination of IGPR-1. The NEDD4-mediated polyubiquitination of IGPR-1 stimulated lysosomal degradation of IGPR-1 as the treatment of cells with the lysosomal inhibitors, bafilomycine and ammonium chloride increased IGPR-1 levels in the HEK-293 cells ectopically expressing IGPR-1 and in multiple human skin melanoma cell lines. Hence, these findings suggest that ubiquitin E3 ligase NEDD4 is a key regulator of IGPR-1 with a significant implication in the therapeutic targeting of IGPR-1.

cell biology↗

bioRxiv2020

CD209L/L-SIGN and CD209/DC-SIGN act as receptors for SARS-CoV-2 and are differentially expressed in lung and kidney epithelial and endothelial cells

As the COVID-19 pandemic continues to spread, investigating the processes underlying the interactions between SARS-CoV-2 and its hosts is of high importance. Here, we report the identification of CD209L/L-SIGN and the related protein CD209/DC-SIGN as receptors capable of mediating SARS-CoV-2 entry into human cells. Immunofluorescence staining of human tissues revealed prominent expression of CD209L in the lung and kidney epithelium and endothelium. Multiple biochemical assays using a purified recombinant SARS-CoV-2 spike receptor binding domain (S-RBD) or S1 encompassing both NTB and RBD and ectopically expressed CD209L and CD209 revealed that CD209L and CD209 interact with S-RBD. CD209L contains two N-glycosylation sequons, at sites N92 and N361, but we determined that only site N92 is occupied. Removal of the N-glycosylation at this site enhances the binding of S-RBD with CD209L. CD209L also interacts with ACE2, suggesting a role for heterodimerization of CD209L and ACE2 in SARS-CoV-2 entry and infection in cell types where both are present. Furthermore, we demonstrate that human endothelial cells are permissive to SARS-CoV-2 infection and interference with CD209L activity by knockdown strategy or with soluble CD209L inhibits virus entry. Our observations demonstrate that CD209L and CD209 serve as alternative receptors for SARS-CoV-2 in disease-relevant cell types, including the vascular system. This property is particularly important in tissues where ACE2 has low expression or is absent, and may have implications for antiviral drug development.

cell biology↗

bioRxiv2020

TMIGD1, a putative tumor suppressor, induces G2-M cell cycle checkpoint arrest in colon cancer cells

Colorectal cancer (CRC) is a leading non-familial cause of cancer mortality among men and women. Although various genetic and epigenetic mechanisms have been identified, the full molecular mechanisms deriving CRC tumorigenesis remains incompletely understood. In this study, we demonstrate that cell adhesion molecule transmembrane and immunoglobulin domain containing1 (TMIGD1) is highly expressed in mouse and human normal intestinal epithelial cells. We have developed TMIGD1 knockout mice and show that the loss of TMIGD1 in mice results in the development of adenomas in small intestine and colon. Additionally, the loss of TMIGD1 in mouse impaired intestinal epithelium brush border formation, junctional polarity and maturation. Mechanistically, TMIGD1 inhibits tumor cell proliferation, cell migration, arrests cell cycle at G2/M phase and induces expression of p21CIP1 (cyclin-dependent kinase inhibitor 1), and p27KIP1 (cyclin-dependent kinase inhibitor 1B) expression, key cell cycle inhibitor proteins involved in the regulation of the cell cycle. Moreover, we demonstrate that TMIGD1 is progressively downregulated in sporadic human CRC and correlates with poor overall survival. Our findings identify TMIGD1 as a novel tumor suppressor gene and provide insights into the pathogenesis of colorectal cancer and possibilities as a potential therapeutic target.

cancer biology↗

bioRxiv2020

Cell adhesion molecule IGPR-1 activates AMPK connecting cell adhesion to energy sensing and autophagy

Immunoglobulin (Ig) and proline-rich receptor-1 (IGPR-1) is a cell adhesion molecule that regulates angiogenesis and endothelial barrier function. IGPR-1 is activated by shear stress and mediates endothelial cells response to shear stress. Autophagy plays critical roles in the maintenance of endothelial cells in response to cellular stress caused by blood flow. However, whether IGPR-1 is activated in response to, and mediates autophagy remains unknown. In this study, we demonstrate that IGPR-1 is activated by autophagy inducing stimuli, such as amino acid starvation, nutrient deprivation, rapamycin and lipopolysaccharide (LPS). We have identified I{kappa}B kinase{beta} (IKK{beta}) as a key serine/threonine kinase activated by autophagy stimuli and mediates phosphorylation of IGPR-1 at Ser220. Activation of IGPR-1, in turn, stimulates phosphorylation of AMP-activated protein kinase (AMPK), which leads to phosphorylation of key pro-autophagy proteins, ULK1 and Beclin-1 (BECN1), increased LC3-II levels and accumulation of LC3 punctum. This study demonstrates that IGPR-1 is activated by and regulates autophagy, connecting cell adhesion to autophagy, a finding that has important significance for autophagy-driven pathologies such cardiovascular diseases and cancer.

cell biology↗

bioRxiv2018

Dynamics of Spaetzle morphogen shuttling in the Drosophila embryo shapes pattern

Establishment of morphogen gradients in the early Drosophila embryo is challenged by a diffusible extracellular milieu, and rapid nuclear divisions that occur at the same time. To understand how a sharp gradient is formed within this dynamic environment, we followed the generation of graded nuclear Dorsal (Dl) protein, the hallmark of pattern formation along the dorso-ventral axis, in live embryos. We show that a sharp gradient is formed through extracellular, diffusion-based morphogen shuttling that progresses through several nuclear divisions. Perturbed shuttling in wntD mutant embryos results in a flat activation peak and aberrant gastrulation. Re-entry of Dl into the nuclei at each cycle refines the signaling output, by guiding graded accumulation of the T48 transcript that drives patterned gastrulation. We conclude that diffusion-based ligand shuttling, coupled with dynamic readout, establishes a refined pattern within the diffusible environment of early embryos.

bioinformatics↗