Specificity Protein 1: A Protein With a Two-Sided Role in Ischemic Stroke

Stroke is one of the leading causes of death and disability worldwide. However, there is a lack of effective medications to speed up the recovery process. Ischemic stroke, as the result of cerebral infarction or cerebral artery narrowing, is accompanied by hemiplegia or impaired consciousness. There are many transcription factors involved in the development of this condition, whose alterations can influence or signal the prognostic outcomes of ischemic stroke. Among them, the augmented expression of specificity protein 1 (SP1) can participate in the progression of the disease by binding DNA to regulate the transcriptions of many genes. Different studies have provided different answers as to whether SP1 plays a positive or a negative role in ischemic stroke. On the one hand, SP1 can play a cytoprotective role as both an antioxidant and anti-apoptotic agent for neurons and glial cells. On the other hand, it can also damage neuronal cells by promoting inflammation and exacerbating brain edema. In this review, we highlight the roles of SP1 in ischemic stroke and shed light on the underlying mechanism.

High Glucose Reduces the Paracellular Permeability of the Submandibular Gland Epithelium via the MiR-22-3p/Sp1/Claudin Pathway

Tight junctions (TJs) play an important role in water, ion, and solute transport through the paracellular pathway of epithelial cells; however, their role in diabetes-induced salivary gland dysfunction remains unknown. Here, we found that the TJ proteins claudin-1 and claudin-3 were significantly increased in the submandibular glands (SMGs) of db/db mice and high glucose (HG)-treated human SMGs. HG decreased paracellular permeability and increased claudin-1 and claudin-3 expression in SMG-C6 cells. Knockdown of claudin-1 or claudin-3 reversed the HG-induced decrease in paracellular permeability. MiR-22-3p was significantly downregulated in diabetic SMGs and HG-treated SMG-C6 cells. A miR-22-3p mimic suppressed claudin-1 and claudin-3 expression and abolished the HG-induced increases in claudin-1 and claudin-3 levels in SMG-C6 cells, whereas a miR-22-3p inhibitor produced the opposite effects. Specificity protein-1 (Sp1) was enhanced in diabetic SMGs and HG-treated SMG-C6 cells, which promoted claudin-1 and claudin-3 transcription through binding to the corresponding promoters. A luciferase reporter assay confirmed that miR-22-3p repressed Sp1 by directly targeting the Sp1 mRNA 3′-untranslated region (3′-UTR). Consistently, the miR-22-3p mimic suppressed, whereas the miR-22-3p inhibitor enhanced, the effects of HG on Sp1 expression. Taken together, our results demonstrate a new regulatory pathway through which HG decreases the paracellular permeability of SMG cells by inhibiting miR-22-3p/Sp1-mediated claudin-1 and claudin-3 expression.

Insilico Search for Potential DNA Binding Domain of Human Zinc Finger Protein Sp1

Specificity protein 1 (Sp1) belongs to a family of ubiquitously expressed, C2H2-type zinc finger-containing DNA binding proteins that activate or repress transcription of many genes in response to physiological and pathological stimuli. Specificity protein 1 is considered to be a constitutively expressed transcription factor and has been implicated in the regulation of a wide variety of housekeeping genes, tissue-specific genes, and genes involved in the regulation of growth. In order to determine the binding affinity of Sp1 zinc finger domains, the total energy for each and every possible combination of GC box and Zn finger motifs using Hex server, Model IT software’s is calculated. According to the findings of this study, the design of multi-zinc finger proteins with a variety of sequence specificities will be easier to accomplish. Among the three motifs present in Specificity protein 1, motifs 1 and 2 have higher binding affinity than motif 3.

Enhanced Sp1/YY1 Expression Directs CBS Transcription to Mediate VEGF-Stimulated Pregnancy-Dependent H 2 S Production in Human Uterine Artery Endothelial Cells

Pregnancy and VEGF (vascular endothelial growth factor) stimulate uterine artery endothelial cell (UAEC) hydrogen sulfide production via selectively upregulating CBS (cystathionine β-synthase) but not CSE (cystathionine γ-lyase) expression. This study was conducted to determine the mechanisms by which VEGF utilizes to stimulate pregnancy-dependent upregulation of CBS and hydrogen sulfide production in human UAEC. The proximal human CBS promoter contains 4 Sp1 (specificity protein 1; a/b/c/d) sites and 1 YY1 (Yin Yang 1) site; luciferase assays using reporter genes driven by human CBS promoter with a series of 5′-deletions identified a promoter sequence (−574 to −394) containing Sp1d and the YY1 sites critical for basal and VEGF-stimulated CBS promoter activation. VEGF stimulated pregnancy-dependent recruitment of Sp1 to Sp1d and YY1 to YY1 and also recruited YY1 to Sp1c and increased Sp1/YY1 association in pregnant human UAEC, suggesting formation of a Sp1/YY1 complex at the Sp1c site. Endothelial Sp1 and YY1 proteins were significantly greater in pregnant than nonpregnant human uterine artery. VEGF stimulated pregnancy-dependent Sp1 and YY1 protein expression in vitro. Treatment with Sp1 and YY1 siRNAs completely blocked Sp1/YY1-mediated pregnancy-dependent CBS protein upregulation and hydrogen sulfide production by VEGF in human UAEC. VEGF did not trans -activate CSE promoter or increase CSE expression, and Sp1/YY1 knockdown did not affect CSE expression in human UAEC. Thus, pregnancy augments EC Sp1 and YY1 expression and promotes the recruitment of Sp1/YY1 to their DNA-binding sequences in proximal human CBS promoter to upregulate CBS transcription, underlying a novel mechanism to mediate VEGF-stimulated pregnancy-dependent endothelial hydrogen sulfide production in the human uterine artery.