Disease relevance of GJA1

• We previously showed that Cx26 and Cx43 overexpressed in MDA-MB-231 breast cancer cells inhibited tumor growth in vivo but not in two-dimensional cultures [1].
• Furthermore, there was heterogeneous Cx43 expression in the carcinoma cells of 14 of the 27 NST carcinomas and the staining was often intercellular and punctate, characteristic of functional connexins [2].
• Cx43 staining of the myoepithelium was also a feature of the benign lesions and ductal carcinoma in situ (DCIS) [2].
• Similarly, a lobular carcinoma did not express Cx26 or Cx43, but there was punctate Cx43 in the epithelial cells of a mucoid carcinoma [2].
• Immunoblot analysis showed different CX43 isoforms in control cortex and in low-grade gliomas [3].
• Based on these data it is concluded that in patients with heart failure, down-regulation of ZO-1 matches the diminished expression levels of connexin 43, suggesting that ZO-1 plays an important role in gap junction formation and gap junction plaque stability [4].

Psychiatry related information on GJA1

• The distribution of the astrocytic gap junctional protein, connexin43 (Cx43) was compared immunohistochemically with that of amyloid plaques in Alzheimer's Disease (AD) brain [5].

High impact information on GJA1

• Most of these studies utilized cells in tissue culture that expressed a specific gap junction protein, connexin 43 [6].
• Phosphorylation of connexin43 (Cx43) on serine368 (S368) has been shown to decrease gap junctional communication via a reduction in unitary channel conductance [7].
• Our evidence indicates that PKC-dependent phosphorylation of Cx43 at S368 creates dynamic communication compartments that can temporally and spatially regulate wound healing [7].
• We found that outgrowths of human keratinocytes in wounds or epibole cultures display parallel changes in the expression of laminin 5, integrin alpha3beta1, E-cadherin, and the gap junctional protein connexin 43 [8].
• When keratinocytes were adhered on laminin 5, both structural (assembly of connexin 43 in gap junctions) and functional (dye transfer) assays showed a two- to threefold increase compared with collagen and five- to eightfold over fibronectin [8].

Chemical compound and disease context of GJA1

• To elucidate the role of connexins in the progression of prostate cancer from a hormone-dependent to -independent state, we introduced connexin-43 and connexin-32 into an invasive, androgen-independent cell line, PC-3 [9].
• The development of intimal hyperplasia in vitro was decreased in presence of fluvastatin and was associated with reduced Cx43 expression [10].
• Despite the loss of GJC, the ability of the F199L Cx43 mutant to inhibit growth of either Cx43-/- cells or two cancer cell lines, HeLa and C6 glioma cells, was similar to that of the wild-type Cx43 [11].
• Furthermore, coinfection of Sf-9 cells with recombinant baculoviruses encoding pp60v-src and Cx43 resulted in the accumulation of phosphotyrosine in Cx43 [12].
• In the course of performing an N-ethyl-N-nitrosourea mutagenesis screen, we identified a dominant mouse mutation that exhibits many classic symptoms of ODDD, including syndactyly, enamel hypoplasia, craniofacial anomalies and cardiac dysfunction [13].

Biological context of GJA1

• Connexin 43 (GJA1) mutations cause the pleiotropic phenotype of oculodentodigital dysplasia [14].
• The human connexin 43 gene, or GJA1, is located at human chromosome 6q22-q23 within the candidate region for the oculodentodigital dysplasia locus [14].
• Several laboratories have mapped the human gap junction protein subunit, connexin43 (locus designation, GJA1), to overlapping regions of chromosome 6, localizing GJA1 to 6q14-->q24 [15].
• A GJA1-related pseudogene GJA1P was assigned to chromosome 5 [16].
• Molecular genetic studies revealed a novel GJA1 mutation affecting the amino terminus of the gap junction protein alpha-1 (Cx43) [17].

Anatomical context of GJA1

• OBJECTIVES: To describe a Brazilian family with oculodentodigital dysplasia (ODDD) and to screen for mutations in the gap junction protein alpha 1 (GJA1) gene in this family [18].
• Furthermore, secreted factors from connexin overexpressing cells inhibited endothelial cell tubulogenesis and migration, and xenografts of Cx43 overexpressing MDA-MB-231 cells showed reduced tumor angiogenesis [1].
• In the current study, we show that overexpression of Cx26 or Cx43 has tumor-suppressive properties in a three-dimensional environment such that they reduced anchorage-independent cell growth and induced partial redifferentiation of three-dimensional organoids of MDA-MB-231 cells [1].
• Intercellular calcium waves in HeLa cells expressing GFP-labeled connexin 43, 32, or 26 [19].
• The aequorin partner of the connexin 43 chimera reported calcium levels in COS-7 cells in at least two different calcium environments [20].

Associations of GJA1 with chemical compounds

• A new mutation in the GJA1 gene was identified, consisting of a change from proline to histidine at codon 59 [18].
• Stimulation in vitro of T and B lymphocytes with phytohaemagglutinin (PHA) and lipopolysaccharide (LPS), respectively, increased Cx40 and Cx43 protein expression [21].
• Cx43del(130-136) and Cx43 co-localized by immunofluorescence and were co-purified from Triton X-100-solubilized cell extracts [22].
• Regarding the role of calcium, the content in both Cx40 and Cx43 was decreased in cultured neonatal rat cardiomyocytes after 24 h administration of 100 nM verapamil [23].
• Interestingly, endothelin-1 and angiotensin-II increased Cx43 but did not affect Cx40 expression [23].
• We conclude that activation of the EGFR pathway in response to HP leads to decrease of GJIC via tyrosine phosphorylation of Cx43 in ONH astrocytes [24].

Physical interactions of GJA1

• Here we show that Cx43 binds alpha-tubulin equally well as beta-tubulin [25].
• In HEK293 cells, by contrast, a connexin-43 mutant lacking the Src phosphorylation site (Tyr265) interacted with ZO-1 despite cotransfection of a constitutively active c-Src [26].
• Cx43 antiserum could also coprecipitate ZO-1 in the transfected and untransfected ROS cells [27].

Enzymatic interactions of GJA1

• Activated BMK1 selectively phosphorylates Cx43 on Ser-255 in vitro and in vivo, but not on S279/S282, which are reported as the consensus phosphorylation sites for MAPK [28].
• Our results support a model in which activated c-Src phosphorylates the COOH-terminal tail of Cx43 on residue Tyr(265), resulting in a stable interaction between both proteins leading to inhibition of gap junctional communication [29].

Co-localisations of GJA1

• Because connexin45 (Cx45) has been shown to colocalize with Cx43, we determined whether the number, size, or distribution of Cx45 gap junctions is altered in the failing heart [30].

Regulatory relationships of GJA1

• In contrast, in humans suffering from atrial fibrillation (AF), the content in Cx40 can be enhanced while Cx43 was unaltered, although in several other studies, other changes of the cardiac connexins were found, which might be related to the type of AF [23].
• Connexin 43 suppresses human glioblastoma cell growth by down-regulation of monocyte chemotactic protein 1, as discovered using protein array technology [31].
• To determine whether this released Ca2+ propagates through gap junctions to neighboring cells and thereby constitutes a long range signaling network, we developed a cell system in which cells expressing both connexin-43 and ryanodine receptor are surrounded by cells expressing only connexin-43 [32].
• In HeLa cells, SNAP did not reduce dye transfer of cells expressing Cx43, but decreased the dye transfer from Cx37-expressing cells to Cx43-expressing cells by 76% [33].
• In the present study it is shown that 12-O-tetradecanoylphorbol-13-acetate (TPA) and EGF induce similar phosphorylation pattern of the gap junction protein connexin43 (Cx43) in K7 cells, although their effects on GJIC are opposite [34].

Other interactions of GJA1

• In summary, Cx26 and Cx43 inhibit the malignant properties of MDA-MB-231 cells via GJIC-independent mechanisms, including regulation of EMT and angiogenesis [1].
• Furthermore, by co-immunoprecipitation, we found that BMK1 directly associates with Cx43 in vivo [28].
• They constitute separate structures in the Cx32 and Cx43 molecules, the CT domain being an integral part of fast V(j) gating [35].
• Western blot analysis also demonstrated the presence of Cx40 and Cx43 proteins in T and B lymphocytes in a manner coincidental to the mRNA detection [21].
• Atrial gap junctions were larger than nodal junctions and contained moderate amounts of Cx40, Cx43, and Cx45 [36].

Analytical, diagnostic and therapeutic context of GJA1

• Results from immunofluorescence and Northern blot analysis revealed that, of the panel of connexins examined, only Cx43 was variably expressed in these cell lines in vitro [37].
• We demonstrate a loss of Cx43 staining at the wound margins during initial wound healing and after transplantation of keratinocytes [38].
• Molecular dissection of transjunctional voltage dependence in the connexin-32 and connexin-43 junctions [35].
• Immunofluorescent staining and laser scanning confocal microscopy showed that Cx43 was strongly expressed in the corneal and limbal suprabasal epithelial cells, but the basal cells of the limbal epithelium were negative [39].
• Using GAP11, a rabbit polyclonal antibody against the Cx32 extracellular loop 2 (151-187), a sequence that is highly homologous in Cx43, the Cx43(dim) and Cx43(bright) cells were selected from primary limbal epithelial cultures by fluorescence-activated cell sorting and were evaluated for stem cell properties [39].

References