Structural and functional similarities exist between the Drosophila Toll/Cactus/Dorsal signaling pathway and the mammalian cytokine-mediated interleukin-1 receptor (IL-1R)/I-kappaB/NF-kappaB activation cascade. In addition to a role regulating dorsal-ventral polarity in the developing Drosophila embryo, signaling through Drosophila Toll (dToll) activates the nonclonal, or innate, immune response in the adult fly. Toll proteins are single transmembrane proteins with multiple leucine-rich repeats in the extracellular region and the cytoplasmic domain with high homolog to the interleukine-1 receptor.
Recent evidence indicates that human homologues of the fly Toll protein participates in the regulation of both innate and adaptive human immunity through the activation of NF-kappaB and the expression of the NF-kappaB-controlled genes IL-1, IL-6, and IL-8, thus affirming the evolutionary conservation of this host defense pathway. Rock et al. (1998) identified a family of human receptors structurally related to Drosophila Toll.
NCBI Summary:
This gene encodes a member of the toll-like receptor (TLR) family, which plays a fundamental role in pathogen recognition and activation of innate immune responses. These receptors recognize distinct pathogen-associated molecular patterns that are expressed on infectious agents. The protein encoded by this gene recognizes bacterial flagellin, the principal component of bacterial flagella and a virulence factor. The activation of this receptor mobilizes the nuclear factor NF-kappaB, which in turn activates a host of inflammatory-related target genes. Mutations in this gene have been associated with both resistance and susceptibility to systemic lupus erythematosus, and susceptibility to Legionnaire disease.[provided by RefSeq, Dec 2009]
General function
Receptor
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Cellular localization
Plasma membrane
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Ovarian function
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Expression regulated by
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Ovarian localization
Cumulus, Granulosa, Theca
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Abnormal expression of TLRs may play a role in lower embryo quality of women with polycystic ovary syndrome. Gu BX et al. (2016) Toll-like receptors (TLRs) localize in mammalian ovary, including granulosa cells, cumulus cells, and theca cells. Previous studies demonstrated that TLRs may be important for the cumulus-oocyte complex expansion and fertilization. There is no evidence to indicate that the deletion of TLRs will induce infertility; however, the abnormal expression of TLRs may decrease oocyte quality and fertility rate. In the present study, we investigated the effects of polycystic ovary syndrome (PCOS) on the expression of TLRs in cumulus cells by using western-blot and quantitative real-time PCR (qRT-PCR) analyses. We found that the expression of TLR4 and 9 in cumulus cells was influenced significantly by PCOS. We also observed that overweight/obesity changed the expression of TLR2 and 5 in cumulus cells of PCOS subjects. In addition, we found that the rate of available embryos of women with PCOS was slightly lower. These results indicate that the abnormal expression of TLRs in cumulus may be a reason for the lower embryo quality of women with PCOS. ART: assisted reproductive technology BMI: body mass index COC: cumulus-cell-oocyte complex PCOS: polycystic ovary syndrome qRT-PCR: quantitative real-time PCR TLRs: Toll-like receptors.//////////////////
Chaudhary et al. (1998) reported the cloning of two novel human genes, TIL3 and TIL4 (Toll/IL-1R-like-3, -4) that exhibit homology to both the leucine-rich repeat extracellular domains and the IL-1R-like intracellular domains of human and Drosophila Toll. Northern analysis showed distinctly different tissue distribution patterns with TIL3 expressed predominantly in ovary, peripheral blood leukocytes, and prostate.
Changes in the Expression of Toll-Like Receptor mRNAs During Follicular Growth and in Response to Lipopolysaccharide in the Ovarian Follicles of Laying Hens. Subedi K et al. The aim of this study was to determine the changes in the mRNA expression of Toll-like receptors (TLRs) in hen ovarian follicles during follicular growth and in response to lipopolysaccharide (LPS). White follicles and the fifth largest to largest follicles (WF and F(5)-F(1), respectively) were collected from laying hens. To examine the effects of LPS, the laying hens were treated intravenously with LPS (1 mg/kg BW) 0, 3, 6, 12 and 24 h before examination. Expressions of TLRs and IL-1 beta in the theca and granulosa layers were examined by semi-quantitative RT-PCR. Immunocytochemistry was performed to identify immunoreactive TLR-4. The theca layer expressed TLR-2, TLR-4, TLR-5 and TLR-7, whereas the granulosa layer expressed only TLR-4 and TLR-5. The expression of TLR-4 and TLR-5 in the theca layer increased significantly during follicular growth. In the granulosa layer, the expression of TLR-5 increased, but that of TLR-4 was unchanged. Expression of TLR-4 increased significantly during the period of 6 to 12 h of LPS treatment in the theca layer and during the period of 12 to 24 h in the granulosa layer of F(3). Immunoreaction products for TLR-4 were observed in theca interna and granulosa layers of WF and F(5)-F(1), with the greater amount observed in the theca interna. LPS treatment significantly increased expression of IL-1beta in the theca layer after 3 h and in the granulosa layer during the period of 12 to 24 h. These results suggest that TLRs are expressed in ovarian follicles and that TLR-4 and TLR-5 expression increases with the growth of follicles. Enhanced expression of TLR-4 and IL-1beta by LPS in the theca and granulosa layers suggests possible roles of TLR in recognition of microorganisms.