Disease relevance of Gja4

• Here we use total acid extraction and repeated fractionation to isolate and sequence Lewis lung carcinoma (3LL)-specific peptide(s), which shows sequence homology to the connexin 37 protein [1].
• In advanced atheromas, Cx37 was detected in medial smooth muscle cells and in macrophages in the lipid core but not in the endothelium covering the plaques [2].
• METHODS: Using intravital microscopy and the cecal ligation and perforation 24-h model of sepsis, arterioles in the cremaster muscle of male C57BL/6 wild-type (WT), iNOS-/-, eNOS-/-, nNOS-/- and Cx37-/- mice were locally stimulated with KCl to initiate conducted vasoconstriction [3].
• Connexin 37 gene is not mutated in lung carcinomas 3LL and CMT [4].
• A targeted disruption of the gene encoding the gap junction protein connexin37 (Cx37; alpha 4) results in female infertility [5].

High impact information on Gja4

• Using in vivo adoptive transfer, we show that monocyte and macrophage recruitment is enhanced by eliminating expression of Cx37 in these leukocytes but not by eliminating its expression in the endothelium [6].
• We further show that Cx37 hemichannel activity in primary monocytes, macrophages and a macrophage cell line (H36.12j) inhibits leukocyte adhesion [6].
• Here we show that connexin 37 is present in gap junctions between oocyte and granulosa cells and that connexin 37-deficient mice lack mature (Graafian) follicles, fail to ovulate and develop numerous inappropriate corpora lutea [7].
• We have recently isolated tumour-associated antigen (TAA) peptides, MUT 1 and MUT 2, derived from a mutated connexin 37 gap-junction protein, from the malignant 3LL-D122 murine lung carcinoma [8].
• The amino acid sequence of mouse Cx37 is most similar to rat connexin43 (59% identity) and Xenopus connexin38 (66% identity) when compared from the NH2 terminus to the end of the fourth putative transmembrane region [9].

Biological context of Gja4

• In fetal ovary, the mRNA transcripts for 3 more connexins (Cx31, Cx37 and Cx45) were expressed in all the genotypes [10].
• Functional assays of meiotic competence confirm that oocytes from connexin-37-deficient mice are unable to enter M phase (initiate meiotic maturation) unless treated with the phosphatase inhibitor okadaic acid (OA) [11].
• Unlike growing oocytes from heterozygous control animals, OA-treated oocytes from connexin-37-deficient mice respond acutely and progress rapidly to the circular bivalent stage of meiosis I and upon removal from OA rapidly revert to an interphase state [11].
• Mice lacking either connexin37 (Cx37) or connexin40 (Cx40), the predominant gap junction proteins present in vascular endothelium, are viable and exhibit phenotypes that are largely non-blood vessel related [12].
• Of the other six connexin genes which have previously been assigned to a human chromosome, two of these, Cx37 and Cx40, are also found on chromosome 1 [13].

Anatomical context of Gja4

• In heart, Cx37 was expressed exclusively in these cells, which rules out any direct involvement of this Cx in the propagation of electrical activity between myocytes and the synchronization of contractions [14].
• Cx37 was expressed in retinal endothelial cells [15].
• Both connexins 37 and 40 were expressed in extraglomerular mesangial cells, connexin 40 was abundantly expressed in intraglomerular mesangial cells, but connexin 37 was limited to mesangial cells at the vascular pole [16].
• Cx37 immunoreactivity was found in blood vessels of the inner retina [17].
• Acetylated alpha-tubulin and Cx37 double labelling revealed that the majority of Cx37 gap junctions, irrespective of follicle stage, were located on the outer surface of the oocyte cytoskeleton [18].

Associations of Gja4 with chemical compounds

• Cx37 transcripts were also found to increase two to threefold in response to retinoic acid treatment of cultured embryonic carcinoma F9 cells [9].
• These results support the notion that gap junction hemichannels formed of certain connexins are more likely than others to pair functionally with Cx37, and suggest co-transfection strategies that might prove effective in sensitizing tumor cell populations to GCV [19].
• In these cells, mouse Cx37 protein was phosphorylated mainly at serine, less at tyrosine, and very little at threonine residues [20].
• Short-term treatment with simvastatin leads to recovery of Cx37 expression but not Cx40 expression [21].
• Here we have unambiguously demonstrated that clones K(b)39.5 (39.5) and D122 of 3LL, and C6 and E9 of CMT 64, previously employed, have only normal Cx37 sequences, including those of codon 54 [4].

Co-localisations of Gja4

• Connexin 37 was partially colocalized with connexin 43 in tracheal smooth muscle cells, and showed a gradual increase in expression during postnatal development [22].

Regulatory relationships of Gja4

• Apparently, Cx40-deficient endothelial cells upregulate and redistribute Cx37 as a molecular adaptation to the lack of Cx40 [23].

Other interactions of Gja4

• Differential expression and localisation of connexin-37 and connexin-43 in follicles of different stages in the 4-week-old mouse ovary [18].
• Other down-regulated genes included: Cyp19a1, Fshr, Inhb, and the oocyte factors Zp1-3 and Gja4 [24].
• The microvasculature of STZ-induced apoE-deficient mice developed endothelial dysfunction, which may be linked to a decrease in the contribution of the EDHF component due to a decrease in SK2 and 3 and Cx 37 expression [25].
• Immunostaining revealed that during prenatal development Cx37 predominated in endothelial and endocardial cells but was also detectable in small amounts in the trabeculated and compact layers of ventricular myocardium, as well as in the mesenchyme of conotruncal ridges and atrioventricular cushions [26].
• H-2K(b)-restricted tumor epitope peptides, including tyrosinase-related protein 2 residues 181-188 (TRP-2) and connexin 37 residues 52-59 (MUT1), were applied to permeability barrier-disrupted C57BL/6 (B6) mouse skin from which the stratum corneum of the epidermis had been removed by tape-stripping [27].

Analytical, diagnostic and therapeutic context of Gja4

• The purpose of the present study was to localise Cx37 and Cx43 in sections of ovarian mouse follicles of different developmental stage, and compare their relative expression using immunofluorescence and confocal microscopy [18].
• High stringency hybridization of Northern blots with the coding sequence of Cx40 identified a single transcript of 3.5 kb that is at least 16-fold more abundant in lung-similar to mouse Cx37-than in other adult tissues (kidney, heart, and skin) [28].
• Continuous Cx37 expression in granulosa cells was confirmed using RT-PCR [29].
• Comparison of the expression of the principal vascular connexins (Cx37, 40 and 43), implicated in EDHF-mediated dilatation were undertaken by immunohistochemistry [30].

References