scholarly journals 229CHARACTERIZATION OF CONNEXIN 43 IN THE CANINE OVARIAN FOLLICLE

2004 ◽  
Vol 16 (2) ◽  
pp. 235 ◽  
Author(s):  
L.A. Willingham-Rocky ◽  
M.C. Golding ◽  
M.E. Westhusin ◽  
D.C. Kraemer ◽  
R.C. Burghardt
Keyword(s):  
Connexin 43 ◽  
Ovarian Follicle ◽  
Physiological State ◽  
Specific Primers ◽  
Intense Staining ◽  
Antral Follicles ◽  
Junction Protein ◽  
Cx43 Mrna ◽  
Punctate Staining ◽  
Estrus Stage

Connexin 43 (Cx43) is the most abundant gap-junction protein in ovarian follicle cell interactions and has been well characterized for several mammalian species. However, the involvement of Cx43 in canine follicular development has not been extensively investigated. The objective of this study was to 1) characterize the spatial patterns of Cx43 localization within the canine ovarian follicle at various physiological states and during the estrous cycle (prepubertal, anestrus, proestrus, estrus and diestrus), and 2) to characterize the canine Cx43 mRNA transcript. The spatial expression pattern of Cx43 protein was evaluated by immunofluorescence microscopy in canine ovaries. Cx43 was not detected in primordial follicles, but was detected in primary and secondary follicles at each physiological state at all granulosa cell borders. In secondary follicles, definitive, punctate staining patterns were localized along mural granulosa cells and also in the surrounding granulosa-cumulus cell borders. Notably, more intense staining was observed in the corona radiata cells immediately surrounding the oocyte, as well as in trans-zonal projections and at the perivitelline membrane. Patterns of localization were most similar between proestrus and diestrus, and between prepubertal and anestrus in secondary follicles. Estrus-stage follicles showed a decrease in localization at the corona-oocyte cell borders as compared to proestrus and diestrus. In large, healthy antral follicles from proestrus and estrus stages, Cx43 was present in the stroma, theca, and granulosa layers. However, antral follicles from estrus-stage ovaries showed more intense staining in the mural granulosa and theca layers, and less intense in the stroma as compared to those of proestrus stage. The most intense pattern of punctate staining was observed in the corpora lutea of diestrus-stage ovaries. Additionally, gene-specific primers were designed from highly conserved regions of Cx43 mRNA among bovine, human and mouse. RNA was isolated from canine uterus and used as a template for RT-PCR. The PCR products were then sequenced and verified in GenBank to assess homology. The sequenced coding region for canine Cx43 mRNA shares 93% sequence homology with bovine vascular smooth muscle. Canine specific primers for this sequence have been designed, and expression analysis studies in canine ovarian follicles are currently underway. These results indicate that the pattern of localization of Cx43 is similar to that reported for the cow and the pig, except that in canine ovarian preantral follicles, Cx43 is also localized to the peri vitelline membrane. Additionally, these results suggest that the localization of Cx43 is dependent on the physiological state of the ovary, and is likely necessary for folliculogenesis and subsequent oocyte development in canines.

scholarly journals Connexin 43 confers chemoresistance through activating PI3K

Oncogenesis ◽  
2022 ◽  
Vol 11 (1) ◽  
Author(s):  
Kevin J. Pridham ◽  
Farah Shah ◽  
Kasen R. Hutchings ◽  
Kevin L. Sheng ◽  
Sujuan Guo ◽  
...  
Keyword(s):  
Poor Prognosis ◽  
Connexin 43 ◽  
Therapeutic Potential ◽  
Mrna Levels ◽  
Phosphatidylinositol 3 Kinase ◽  
Junction Protein ◽  
Gap Junction Protein ◽  
Cx43 Mrna

AbstractCircumventing chemoresistance is crucial for effectively treating cancer including glioblastoma, a lethal brain cancer. The gap junction protein connexin 43 (Cx43) renders glioblastoma resistant to chemotherapy; however, targeting Cx43 is difficult because mechanisms underlying Cx43-mediated chemoresistance remain elusive. Here we report that Cx43, but not other connexins, is highly expressed in a subpopulation of glioblastoma and Cx43 mRNA levels strongly correlate with poor prognosis and chemoresistance in this population, making Cx43 the prime therapeutic target among all connexins. Depleting Cx43 or treating cells with αCT1–a Cx43 peptide inhibitor that sensitizes glioblastoma to the chemotherapy temozolomide–inactivates phosphatidylinositol-3 kinase (PI3K), whereas overexpression of Cx43 activates this signaling. Moreover, αCT1-induced chemo-sensitization is counteracted by a PI3K active mutant. Further research reveals that αCT1 inactivates PI3K without blocking the release of PI3K-activating molecules from membrane channels and that Cx43 selectively binds to the PI3K catalytic subunit β (PIK3CB, also called PI3Kβ or p110β), suggesting that Cx43 activates PIK3CB/p110β independent of its channel functions. To explore the therapeutic potential of simultaneously targeting Cx43 and PIK3CB/p110β, αCT1 is combined with TGX-221 or GSK2636771, two PIK3CB/p110β-selective inhibitors. These two different treatments synergistically inactivate PI3K and sensitize glioblastoma cells to temozolomide in vitro and in vivo. Our study has revealed novel mechanistic insights into Cx43/PI3K-mediated temozolomide resistance in glioblastoma and demonstrated that targeting Cx43 and PIK3CB/p110β together is an effective therapeutic approach for overcoming chemoresistance.

scholarly journals Luteinizing Hormone-Induced Connexin 43 Down-Regulation: Inhibition of Translation

Endocrinology ◽  
2004 ◽  
Vol 145 (4) ◽  
pp. 1617-1624 ◽  
Author(s):  
Yael Kalma ◽  
Irit Granot ◽  
Dalia Galiani ◽  
Amihai Barash ◽  
Nava Dekel
Keyword(s):  
Connexin 43 ◽  
Ovarian Follicle ◽  
Cell Communication ◽  
Signal Transduction Pathway ◽  
Mapk Signaling ◽  
Down Regulation ◽  
Cx43 Expression ◽  
Mapk Cascades ◽  
Junction Protein

Abstract The coordinated function of the different compartments of the follicle, the oocyte and the somatic cumulus/granulosa cells, is enabled by the presence of a network of cell-to-cell communication generated by gap junctions. Connexin 43 (Cx43) is the most abundant gap junction protein expressed by the ovarian follicle. The expression of Cx43 is subjected to the control of gonadotropins as follows: FSH up-regulates, whereas LH down-regulates its levels. The aim of this study was to explore the mechanism by which LH reduces the levels of Cx43 and to identify the signal transduction pathway involved in this process. The effect of LH was studied in vitro using isolated intact ovarian follicles. The possible mediators of LH-induced Cx43 down-regulation were examined by incubating the follicles with LH in the presence or absence of inhibitors of protein kinase A (PKA) and of MAPK signaling pathways. Our experiments revealed a 3-h half-life of Cx43 in both control and LH-treated follicles, suggesting that LH did not affect the rate of Cx43 degradation. We further demonstrated that the level of Cx43 mRNA was not significantly influenced by this gonadotropin. However, upon LH administration, [35S]methionine incorporation into Cx43 protein was remarkably reduced. The LH-induced arrest of Cx43 synthesis was counteracted by inhibitors of both the PKA and the MAPK cascades. We show herein that LH inhibits Cx43 expression by reducing its rate of translation and that this effect is mediated by both PKA and MAPK.

Phosphorylation of connexin 43 induced by traumatic brain injury promotes exosome release

2018 ◽  
Vol 119 (1) ◽  
pp. 305-311 ◽  
Author(s):  
Wei Chen ◽  
Yijun Guo ◽  
Wenjin Yang ◽  
Lei Chen ◽  
Dabin Ren ◽  
...  
Keyword(s):  
Traumatic Brain Injury ◽  
Brain Injury ◽  
Gap Junction ◽  
Connexin 43 ◽  
Hippocampal Slices ◽  
Long Term Potentiation ◽  
Cx43 Expression ◽  
Term Potentiation ◽  
Junction Protein

Traumatic brain injury (TBI) caused by the external force leads to the neuronal dysfunction and even death. TBI has been reported to significantly increase the phosphorylation of glial gap junction protein connexin 43 (Cx43), which in turn propagates damages into surrounding brain tissues. However, the neuroprotective and anti-apoptosis effects of glia-derived exosomes have also been implicated in recent studies. Therefore, we detected whether TBI-induced phosphorylation of Cx43 would promote exosome release in rat brain. To generate TBI model, adult male Sprague-Dawley rats were subjected to lateral fluid percussion injury. Phosphorylated Cx43 protein levels and exosome activities were quantified using Western blot analysis following TBI. Long-term potentiation (LTP) was also tested in rat hippocampal slices. TBI significantly increased the phosphorylated Cx43 and exosome markers expression in rat ipsilateral hippocampus, but not cortex. Blocking the activity of Cx43 or ERK, but not JNK, significantly suppressed TBI-induced exosome release in hippocampus. Furthermore, TBI significantly inhibited the induction of LTP in hippocampal slices, which could be partially but significantly restored by pretreatment with exosomes. The results imply that TBI-activated Cx43 could mediate a nociceptive effect by propagating the brain damages, as well as a neuroprotective effect by promoting exosome release. NEW & NOTEWORTHY We have demonstrated in rat traumatic brain injury (TBI) models that both phosphorylated connexin 43 (p-Cx43) expression and exosome release were elevated in the hippocampus following TBI. The promoted exosome release depends on the phosphorylation of Cx43 and requires ERK signaling activation. Exosome treatment could partially restore the attenuated long-term potentiation. Our results provide new insight for future therapeutic direction on the functional recovery of TBI by promoting p-Cx43-dependent exosome release but limiting the gap junction-mediated bystander effect.

scholarly journals Involvement of hyaluronan synthesis in ovarian follicle growth in rats

Reproduction ◽  
2014 ◽  
Vol 147 (2) ◽  
pp. 189-197 ◽  
Author(s):  
Noriyuki Takahashi ◽  
Wataru Tarumi ◽  
Bunpei Ishizuka
Keyword(s):  
Ovarian Follicle ◽  
Primary Site ◽  
Corpora Lutea ◽  
Follicular Atresia ◽  
Follicle Growth ◽  
Adult Rats ◽  
Antral Follicles ◽  
Cell Layers ◽  
Ha Synthase

Most of the previous studies on ovarian hyaluronan (HA) have focused on mature antral follicles or corpora lutea, but scarcely on small preantral follicles. Moreover, the origin of follicular HA is unknown. To clarify the localization of HA and its synthases in small growing follicles, involvement of HA in follicle growth, and gonadotropin regulation of HA synthase (Has) gene expression, in this study, perinatal, immature, and adult ovaries of Wistar-Imamichi rats were examined histologically and biochemically and byin vitrofollicle culture. HA was detected in the extracellular matrix of granulosa and theca cell layers of primary follicles and more advanced follicles. Ovarian HA accumulation ontogenetically started in the sex cords of perinatal rats, and its primary site shifted to the intrafollicular region of primary follicles within 5 days of birth. TheHas1–3mRNAs were expressed in the ovaries of perinatal, prepubertal, and adult rats, and the expression levels ofHas1andHas2genes were modulated during the estrous cycle in adult rats and following administration of exogenous gonadotropins in immature acyclic rats. TheHas1andHas2mRNAs were predominantly localized in the theca and granulosa cell layers of growing follicles respectively. Treatments with chemicals known to reduce ovarian HA synthesis induced follicular atresia. More directly, the addition ofStreptomyceshyaluronidase, which specifically degrades HA, induced the arrest of follicle growth in anin vitroculture system. These results indicate that gonadotropin-regulated HA synthesis is involved in normal follicle growth.

Subcellular localization of the Na+/H+ exchanger NHE1 in rat myocardium

1999 ◽  
Vol 276 (2) ◽  
pp. H709-H717 ◽  
Author(s):  
Kevin Petrecca ◽  
Roxana Atanasiu ◽  
Sergio Grinstein ◽  
John Orlowski ◽  
Alvin Shrier
Keyword(s):  
Connexin 43 ◽  
Cell Types ◽  
Ph Homeostasis ◽  
Adult Rat ◽  
Junction Protein ◽  
Close Proximity ◽  
Gap Junction Protein ◽  
Intercalated Disks ◽  
Distinct Distribution ◽  
Intercalated Disk

The Na+/H+exchanger NHE1 isoform is an integral component of cardiac intracellular pH homeostasis that is critically important for myocardial contractility. To gain further insight into its physiological significance, we determined its cellular distribution in adult rat heart by using immunohistochemistry and confocal microscopy. NHE1 was localized predominantly at the intercalated disk regions in close proximity to the gap junction protein connexin 43 of atrial and ventricular muscle cells. Significant labeling of NHE1 was also observed along the transverse tubular systems, but not the lateral sarcolemmal membranes, of both cell types. In contrast, the Na+-K+-ATPase α1-subunit was readily labeled by a specific mouse monoclonal antibody (McK1) along the entire ventricular sarcolemma and intercalated disks and, to a lesser extent, in the transverse tubules. These results indicate that NHE1 has a distinct distribution in heart and may fulfill specialized roles by selectively regulating the pH microenvironment of pH-sensitive proteins at the intercalated disks (e.g., connexin 43) and near the cytosolic surface of sarcoplasmic reticulum cisternae (e.g., ryanodine receptor), thereby influencing impulse conduction and excitation-contraction coupling.

scholarly journals Early disruption of the alveolar-capillary barrier in a ricin-induced ARDS mouse model: neutrophil-dependent and -independent impairment of junction proteins

2019 ◽  
Vol 316 (1) ◽  
pp. L255-L268 ◽  
Author(s):  
Anita Sapoznikov ◽  
Yoav Gal ◽  
Reut Falach ◽  
Irit Sagi ◽  
Sharon Ehrlich ◽  
...  
Keyword(s):  
Connexin 43 ◽  
Early Stage ◽  
Capillary Barrier ◽  
Edema Formation ◽  
Pulmonary Tissue ◽  
Time To Death ◽  
Pulmonary Exposure ◽  
Junction Protein ◽  
Alveolar Capillary ◽  
Junction Proteins

Irrespective of its diverse etiologies, acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) leads to increased permeability of the alveolar-capillary barrier, which in turn promotes edema formation and respiratory failure. We investigated the mechanism of ALI/ARDS lung hyperpermeability triggered by pulmonary exposure of mice to the highly toxic plant-derived toxin ricin. One prominent hallmark of ricin-mediated pulmonary intoxication is the rapid and massive influx of neutrophils to the lungs, where they contribute to the developing inflammation yet may also cause tissue damage, thereby promoting ricin-mediated morbidity. Here we show that pulmonary exposure of mice to ricin results in the rapid diminution of the junction proteins VE-cadherin, claudin 5, and connexin 43, belonging, respectively, to the adherens, tight, and gap junction protein families. Depletion of neutrophils in ricin-intoxicated mice attenuated the damage caused to these junction proteins, alleviated pulmonary edema, and significantly postponed the time to death of the intoxicated mice. Inhibition of matrix metalloproteinase (MMP) activity recapitulated the response to neutrophil depletion observed in ricin-intoxicated mice and was associated with decreased insult to the junction proteins and alveolar-capillary barrier. However, neutrophil-mediated MMP activity was not the sole mechanism responsible for pulmonary hyperpermeability, as exemplified by the ricin-mediated disruption of claudin 18, via a neutrophil-independent mechanism involving tyrosine phosphorylation. This in-depth study of the early stage mechanisms governing pulmonary tissue integrity during ALI/ARDS is expected to facilitate the tailoring of novel therapeutic approaches for the treatment of these diseases.

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