Constitutive localization of the gonadotropin-releasing hormone (GnRH) receptor to low density membrane microdomains is necessary for GnRH signaling to ERK

Specialized membrane microdomains known as lipid rafts are thought to contribute to G-protein coupled receptor (GPCR) signaling by organizing receptors and their cognate signaling molecules into discrete membrane domains. To determine if the GnRHR, an unusual member of the GPCR superfamily, partitions into lipid rafts, homogenates of alpha T3-1 cells expressing endogenous GnRHR or Chinese hamster ovary cells expressing an epitope-tagged GnRHR were fractionated through a sucrose gradient. We found the GnRHR and c-raf kinase constitutively localized to low density fractions independent of hormone treatment. Partitioning of c-raf kinase into lipid rafts was also observed in whole mouse pituitary glands. Consistent with GnRH induced phosphorylation and activation of c-raf kinase, GnRH treatment led to a decrease in the apparent electrophoretic mobility of c-raf kinase that partitioned into lipid rafts compared with unstimulated cells. Cholesterol depletion of alpha T3-1 cells using methyl-beta-cyclodextrin disrupted GnRHR but not c-raf kinase association with rafts and shifted the receptor into higher density fractions. Cholesterol depletion also significantly attenuated GnRH but not phorbol ester-mediated activation of extracellular signal-related kinase (ERK) and c-fos gene induction. Raft localization and GnRHR signaling to ERK and c-Fos were rescued upon repletion of membrane cholesterol. Thus, the organization of the GnRHR into low density membrane microdomains appears critical in mediating GnRH induced intracellular signaling.     

Differential impact of intracellular carboxyl terminal domains on lipid raft localization of the murine gonadotropin-releasing hormone receptor

The mammalian type I GNRH receptor (GNRHR) is unique among G protein-coupled receptors (GPCRs) because of the absence of an intracellular C-terminus. Previously, we have found that the murine GNRHR is constitutively localized to low-density membrane microdomains termed lipid rafts. As such, association of the GNRHR with lipid rafts may reflect both a loss (C-terminus) and a gain (raft association address) of structural characteristics. To address this, we fused either the full-length C-terminus from the nonraft-associated LH receptor (LHCGR; GNRHR-LF) or a truncated (t631) LHCGR C-terminus to the GNRHR. These chimeric receptors are trafficked to the plasma membrane, bind ligand, and display increased agonist-induced receptor internalization, but they do not partition into lipid rafts. Thus, a heterologous C-terminus from a nonraft-associated GPCR redirects localization of the GNRHR to nonraft domains. In contrast to the murine GNRHR, the catfish GNRHR (cfGNRHR) possesses an intracellular C-terminus. We found that the cfGNRHR was localized to lipid rafts and that the cfGNRHR C-terminus did not alter raft localization of the mammalian receptor. Consistent with placement in different lipid microenvironments within the plasma membrane, fluorescence recovery after photobleaching revealed different lateral diffusion phenotypes of the raft-associated GNRHR and cfGNRHR versus the nonraft-associated GNRHR-LF fusion protein. We conclude that whereas an intracellular C-terminus is capable of redirecting the GNRHR to nonraft compartments, this is not a generalized feature of GPCR C-terminal tails. Thus, constitutive raft localization of the GNRHR is not simply a result of the loss of an intracellular C-terminus.     

蒙药乌力吉-18对大鼠下丘脑-垂体-卵巢轴相关激素及受体表达的影响

目的:探讨蒙药乌力吉-18对大鼠下丘脑-垂体-卵巢轴相关激素及受体的影响。方法:选取40只健康雌性未孕SD大鼠,随机分为空白组、对照组、乌力吉-18高、低2个剂量组,每组10只。空白组灌胃等体积蒸馏水,对照组灌胃逍遥丸,高、低剂量组分别灌胃2.0 g·kg^-1·d^-1、1.0 g·kg^-1·d^-1乌力吉-18,连续给药31学艺术d。采用酶联免疫吸附法测定血清促性腺激素释放激素(GnRH)、促卵泡生成素(FSH)、黄体生成素(LH)、雌二醇(E₂)及孕酮(PROG)的含量;免疫组化法检测下丘脑组织促性腺激素释放激素(GnRH)、垂体组织促性腺激素释放激素受体(GnRHR)的表达;以蛋白免疫印迹技术检测卵巢组织促卵泡生成素受体(FSHR)、黄体生成素受体(LHR)蛋白表达量。以实时荧光定量PCR检测卵巢组织中FSHR、LHR基因表达量。结果:与空白组比较,乌力吉-18低剂量组可明显升高血清LH含量(P<0.05),上调下丘脑组织GnRH、垂体组织GnRHR表达及卵巢组织FSHR、LHR蛋白表达(P<0.05);乌力吉-18高剂量组可显著升高血清FSH、LH、E₂含量(P<0.05),上调下丘脑组织GnRH表达及卵巢组织FSHR表达量(P<0.05),并可显著升高卵巢组织中FSHR、LHR基因表达量(P<0.05);对照组可明显升高血清E₂含量(P<0.05)。结论:蒙药乌力吉-18可明显升高血清FSH、LH及E₂的含量,促进下丘脑组织GnRH、垂体组织GnRHR及卵巢组织中FSHR、LHR的表达,表明乌力吉-18能够对下丘脑-垂体-卵巢轴相关激素及受体表达产生影响。     

Signaling complexes associated with the type I gonadotropin-releasing hormone (GnRH) receptor: colocalization of extracellularly regulated kinase 2 and GnRH receptor within membrane rafts

Our previous work demonstrated that the type I GnRH receptor (GnRHR) resides exclusively and constitutively within membrane rafts in alphaT3-1 gonadotropes and that this association was necessary for the ability of the receptor to couple to the ERK signaling pathway. G(alphaq), c-raf, and calmodulin have also been shown to reside in this compartment, implicating a raft-associated multiprotein signaling complex as a functional link between the GnRHR and ERK signaling. In the studies reported here, we used subcellular fractionation and coimmunoprecipitation to analyze the behavior of ERKs with respect to this putative signaling platform. ERK 2 associated partially and constitutively with low-density membranes both in alphaT3-1 cells and in whole mouse pituitary. Cholesterol depletion of alphaT3-1 cells reversibly blocked the association of both the GnRHR and ERKs with low-density membranes and uncoupled the ability of GnRH to activate ERK. Analysis of the kinetics of recovery of ERK inducibility after cholesterol normalization supported the conclusion that reestablishment of the association of the GnRHR and ERKs with the membrane raft compartment was not sufficient for reconstitution of signaling activity. In alphaT3-1 cells, the GnRHR and ERK2 coimmunoprecipitated from low-density membrane fractions prepared either in the presence or absence of detergent. The GnRHR also partitioned into low-density, detergent-resistant membrane fractions in mouse pituitary and coimmunoprecipitated with ERK2 from these fractions. Collectively, these data support a model in which coupling of the GnRHR to the ERK pathway in gonadotropes involves the assembly of a multiprotein signaling complex in association with specialized microdomains of the plasma membrane.     

Casein kinase II sites in the intracellular C-terminal domain of the thyrotropin-releasing hormone receptor and chimeric gonadotropin-releasing hormone receptors contribute to beta-arrestin-dependent internalization

We have previously shown that the mammalian gonadotropin-releasing hormone receptor (GnRHR), a unique G-protein-coupled receptor (GPCR) lacking an intracellular carboxyl tail (C-tail), does not follow a beta-arrestin-dependent internalization pathway. However, internalization of a chimeric GnRHR with the thyrotropin-releasing hormone receptor (TRHR) C-tail does utilize beta-arrestin. Here, we have investigated the sites within the intracellular C-tail domain that are important for conferring beta-arrestin-dependent internalization. In contrast to the chimeric GnRHR with a TRHR C-tail, a chimeric GnRHR with the catfish GnRHR C-tail is not beta-arrestin-dependent. Sequence comparisons between these chimeric receptors show three consensus phosphorylation sites for casein kinase II (CKII) in the TRHR C-tail but none in the catfish GnRHR C-tail. We thus investigated a role for CKII sites in determining GPCR internalization via beta-arrestin. Sequential introduction of three CKII sites into the chimera with the catfish C-tail (H354D,A366E,G371D) resulted in a change in the pattern of receptor phosphorylation and beta-arrestin-dependence, which only occurred when all three sites were introduced. Conversely, mutation of the putative CKII sites (T365A,T371A,S383A) in the C-tail of a beta-arrestin-sensitive GPCR, the TRHR, resulted in decreased receptor phosphorylation and a loss of beta-arrestin-dependence. Mutation of all three CKII sites was necessary before a loss of beta-arrestin-dependence was observed. Visualization of beta-arrestin/GFP redistribution confirmed a loss or gain of beta-arrestin sensitivity for receptor mutants. Internalization of receptors without C-tail CKII sites was promoted by a phosphorylation-independent beta-arrestin mutant (R169E), suggesting that these receptors do not contain the necessary phosphorylation sites required for beta-arrestin-dependent internalization. Apigenin, a specific CKII inhibitor, blocked the increase in receptor internalization by beta-arrestin, thus providing further support for the involvement of CKII. This study presents evidence of a novel role for C-tail CKII consensus sites in targeting these GPCRs to the beta-arrestin-dependent pathway.     

Restricted localization of the TNF receptor CD120a to lipid rafts: a novel role for the death domain

The TNF-alpha receptor, CD120a, has recently been shown to be localized to both plasma membrane lipid rafts and to the trans Golgi complex. Through a combination of both confocal microscopy and sucrose density gradient ultracentrifugation, we show that amino acid sequences located within the death domain (DD) of CD120a are both necessary and sufficient to promote the appropriate localization of the receptor to lipid rafts. Deletion of the DD (CD120a.Delta321-425) prevented the receptor from being targeted to lipid rafts and resulted in a uniform plasma membrane localization. A similar loss of raft localization was also observed following pairwise deletion of the six alpha-helices that comprise the DD. In all situations, the loss of the ability of CD120a to become localized to lipid rafts following mutagenesis was paralleled by a failure of the receptor to initiate apoptosis. Furthermore, introduction of the lpr mutation into CD120a (CD120a.L351N) also resulted in both a loss in the ability of the receptor to signal apoptosis and to be appropriately localized to rafts. In contrast to CD120a, CD120b, which lacks a DD, is mainly expressed in the bulk plasma membrane and to a lesser extent in lipid rafts, but is absent from the Golgi complex. However, a chimeric receptor in which the DD of CD120a was fused to the cytoplasmic domain of CD120b was predominantly localized to lipid rafts. Collectively, these findings suggest that in addition to its role in CD120a signaling, an appropriately folded and functionally active DD is required for the localization of the receptor to lipid rafts.     

Localization of receptors in lipid rafts can inhibit signal transduction

Processes of cell survival, division, differentiation, and death are guided by the binding of signal molecules to receptors, which activates intracellular signaling networks and ultimately elicits genetic, biochemical, or biomechanical responses within the cell. While intracellular mechanisms for these processes have been well studied, little attention has been given to the role extracellular ligand transport and binding may play in signal initiation. Recent studies have found that the localization of receptors in lipid rafts is critical for the functions of many signaling pathways. By concentrating membrane components, rafts may promote essential interactions for signaling. Lipid rafts can also have negative effects on signaling, but mechanisms remain elusive. We propose that raft-mediated receptor clustering can reduce signaling by prolonging the diffusion of ligands to their receptors. We quantify this effect using a simple diffusion-limited binding model that accounts for the spatial distribution of lipid rafts and receptors on the cell surface. We find that receptor clustering can reduce the apparent rate of receptor binding by up to 80%, consistent with observed increases in epidermal growth factor (EGF) binding by up to 100% following disruption of lipid rafts (Pike and Casey 2002 Biochemistry 41:10315-10322; Roepstorff et al. 2002 J Biol Chem 277:18954-18960). Failure to account for the effects of receptor clustering on rates of ligand binding can skew the interpretation of current methods of cancer diagnosis and treatment. Finally, we discuss how the activation of particular signaling pathways can change over time, depending, in part, on the overall level and spatial distribution of the receptors.     

The extracellular domain of luteinizing hormone receptor dictates its efficiency of maturation

The processing of luteinizing hormone receptor (LHR) shows marked differences in different species. While the human LHR is predominantly expressed as the mature, 90 kDa species, rat LHR exists mostly in the 70 kDa precursor form. Since the extracellular domain of the LHR is unusually large in comparison with other G protein-coupled receptors, the present studies examined the role of extracellular domain in its processing. FLAG-tagged chimeric LH receptors were constructed by substituting the extracellular domain of the human receptor in rat LHR (hrr) and the extracellular domain of the rat receptor in human LHR (rhh). The intracellular processing, ligand binding and recycling of the chimeric receptors were compared with that of the wild type receptors in 293T cells. The results showed that the human and rat LHR were expressed predominantly as 90 and 70 kDa species, respectively, as expected. The introduction of the rat extracellular domain into the human LHR (rhh) decreased the abundance of the mature form with an increase in the precursor form. Conversely, substitution of the extracellular domain of the rat LHR by the extracellular domain of the human LHR (hrr) led to an increase in the mature form with a corresponding decrease in the precursor form. Changes were also observed in the ligand binding and recycling of the wild type and chimeric receptors. These results suggest that the extracellular domain of the LHR is one of the determinants that confer its ability for proper maturation and cell surface expression.     

Epidermal growth factor receptors are localized to lipid rafts that contain a balance of inner and outer leaflet lipids: a shotgun lipidomics study

The epidermal growth factor (EGF) receptor partitions into lipid rafts made using a detergent-free method, but is extracted from low density fractions by Triton X-100. By screening several detergents, we identified Brij 98 as a detergent in which the EGF receptor is retained in detergent-resistant membrane fractions. To identify the difference in lipid composition between those rafts that harbored the EGF receptor (detergent-free and Brij 98-resistant) and those that did not (Triton X-100-resistant), we used multidimensional electrospray ionization mass spectrometry to perform a lipidomics study on these three raft preparations. Although all three raft preparations were similarly enriched in cholesterol, the EGF receptor-containing rafts contained more ethanolamine glycerophospholipids and less sphingomyelin than did the non-EGF receptor-containing Triton X-100 rafts. As a result, the detergent-free and Brij 98-resistant rafts exhibited a balance of inner and outer leaflet lipids, whereas the Triton X-100 rafts contained a preponderance of outer leaflet lipids. Furthermore, in all raft preparations, the outer leaflet phospholipid species were significantly different from those in the bulk membrane, whereas the inner leaflet lipids were quite similar to those found in the bulk membrane. These findings indicate that the EGF receptor is retained only in rafts that exhibit a lipid distribution compatible with a bilayer structure and that the selection of phospholipids for inclusion into rafts occurs mainly on the outer leaflet lipids.     

A role for lipid rafts in immune cell signaling

Cross-linking of surface receptors in hematopoietic cells results in the enrichment of these receptors in the rafts along with other downstream signaling molecules. A possible explanation how signal is transduced through the plasma membrane has arisen from the concept of raft. From the study of cellular responses in the plasma membrane which enrich members of the Src-family tyrosine kinase, rafts can function as centers of signal transduction by forming patches. Under physiological conditions, these elements synergize to transduce successfully a signal at the plasma membrane. Rafts are suggested to be important in controlling appropriate protein interactions in hematopoietic cells, and aggregation of rafts following receptor ligation may be a general mechanism for promoting immune cell signaling.     

Differential regulation of TNF-R1 signaling: lipid raft dependency of p42mapk/erk2 activation, but not NF-kappaB activation

The TNFR, TNF-R1, is localized to lipid raft and nonraft regions of the plasma membrane. Ligand binding sets in motion signaling cascades that promote the activation of p42(mapk/erk2) and NF-kappaB. However, the role of receptor localization in the activation of downstream signaling events is poorly understood. In this study, we investigated the dynamics of TNF-R1 localization to lipid rafts and the consequences of raft localization on the activation of p42(mapk/erk2) and NF-kappaB in primary cultures of mouse macrophages. Using sucrose density gradient ultracentrifugation and a sensitive ELISA to detect TNF-R1, we show that TNF-R1 is rapidly and transiently recruited to lipid rafts in response to TNF-alpha. Disruption of lipid rafts by cholesterol depletion prevented the TNF-alpha-dependent recruitment of TNF-R1 to lipid rafts and inhibited the activation of p42(mapk/erk2), while the activation of NF-kappaB was unaffected. In addition, phosphorylated p42(mapk/erk2), but not receptor interacting protein, I-kappaB kinase-gamma, or I-kappaBalpha was detected in raft-containing fractions following TNF-alpha stimulation. These findings suggest that TNF-R1 is localized to both lipid raft and nonraft regions of the plasma membrane and that each compartment is capable of initiating different signaling responses. We propose that segregation of TNF-R1 to raft and nonraft regions of the plasma membrane contributes to the diversity of signaling responses initiated by TNF-R1.     

Lipid rafts regulate cellular CD40 receptor localization in vascular endothelial cells

Cholesterol enriched lipid rafts are considered to function as platforms involved in the regulation of membrane receptor signaling complex through the clustering of signaling molecules. In this study, we tested whether these specialized membrane microdomains affect CD40 localization in vitro and in vivo. Here, we provide evidence that upon CD40 ligand stimulation, endogenous and exogenous CD40 receptor is rapidly mobilized into lipid rafts compared with unstimulated HAECs. Efficient binding between CD40L and CD40 receptor also increases amounts of CD40 protein levels in lipid rafts. Deficiency of intracellular conserved C terminus of the CD40 cytoplasmic tail impairs CD40 partitioning in raft. Raft disorganization after methyl-beta-cyclodextrin treatment diminishes CD40 localization into rafts. In vivo studies show that elevation of circulating cholesterol in high-cholesterol fed rabbits increases the cholesterol content and CD40 receptor localization in lipid rafts. These findings identify a physiological role for membrane lipid rafts as a critical regulator of CD40-mediated signal transduction and raise the possibility that certain pathologic conditions may be treated by altering CD40 signaling with drugs affecting its raft localization.     

Molecular dynamics and interactions for creation of stimulation-induced stabilized rafts from small unstable steady-state rafts

We have evaluated the sizes and lifetimes of rafts in the plasma membrane from the existing literature, with a special attention paid to their intrinsically broad distributions and the limited time and space scales that are covered by the observation methods used for these studies. Distinguishing the rafts in the steady state (reserve rafts) from those after stimulation or unintentional crosslinking of raft molecules (stabilized receptor-cluster rafts) is critically important. In resting cells, the rafts appear small and unstable, and the consensus now is that their sizes are smaller than the optical diffraction limit (250 nm). Upon stimulation, the raft-preferring receptors are clustered, inducing larger, stabilized rafts, probably by coalescing small, unstable rafts or cholesterol-glycosphingolipid complexes in the receptor clusters. This receptor-cluster-induced conversion of raft types may be caused by suppression of alkyl chain isomerization and the lipid lateral diffusion in the cluster, with the aid of exclusion of cholesterol from the bulk domain and the boundary region of the majority of transmembrane proteins. We critically inspected the possible analogy to the boundary lipid concept. Finally, we propose a hypothesis for the coupling of GPI-anchored receptor signals with lipid-anchored signaling molecules in the inner-leaflet raft.     

Dynamic reorganization of chemokine receptors, cholesterol, lipid rafts, and adhesion molecules to sites of CD4 engagement

T cell polarization and redistribution of cellular components are critical to processes such as activation, migration, and potentially HIV infection. Here, we investigate the effects of CD4 engagement on the redistribution and localization of chemokine receptors, CXCR4 and CCR5, adhesion molecules, and lipid raft components including cholesterol, GM1, and glycosyl-phosphatidylinositol (GPI)-anchored proteins. We demonstrate that anti-CD4-coated beads (alpha CD4-B) rapidly induce co-capping of chemokine receptors as well as GPI-anchored proteins and adhesion molecules with membrane cholesterol and lipid rafts on human T cell lines and primary T cells to the area of bead-cell contact. This process was dependent on the presence of cellular cholesterol, cytoskeletal reorganization, and lck signaling. Lck-deficient JCaM 1.6 cells failed to cap CXCR4 or lipid rafts to alpha CD4-B. Biochemical analysis reveals that CXCR4 and LFA-1 are recruited to lipid rafts upon CD4 but not CD45 engagement. Furthermore, we also demonstrate T cell capping of both lipid rafts and chemokine receptors at sites of contact with HIV-infected cells, despite the binding of an HIV inhibitory mAb to CXCR4. We conclude that cell surface rearrangements in response to CD4 engagement may serve as a means to enhance cell-to-cell signaling at the immunological synapse and modulate chemokine responsiveness, as well as facilitate HIV entry and expansion by synaptic transmission.     

A novel biotinylated lipid raft reporter for electron microscopic imaging of plasma membrane microdomains

The submicroscopic spatial organization of cell surface receptors and plasma membrane signaling molecules is readily characterized by electron microscopy (EM) via immunogold labeling of plasma membrane sheets. Although various signaling molecules have been seen to segregate within plasma membrane microdomains, the biochemical identity of these microdomains and the factors affecting their formation are largely unknown. Lipid rafts are envisioned as submicron membrane subdomains of liquid ordered structure with differing lipid and protein constituents that define their specific varieties. To facilitate EM investigation of inner leaflet lipid rafts and the localization of membrane proteins therein, a unique genetically encoded reporter with the dually acylated raft-targeting motif of the Lck kinase was developed. This reporter, designated Lck-BAP-GFP, incorporates green fluorescent protein (GFP) and biotin acceptor peptide (BAP) modules, with the latter allowing its single-step labeling with streptavidin-gold. Lck-BAP-GFP was metabolically biotinylated in mammalian cells, distributed into low-density detergent-resistant membrane fractions, and was readily detected with avidin-based reagents. In EM images of plasma membrane sheets, the streptavidin-gold-labeled reporter was clustered in 20-50 nm microdomains, presumably representative of inner leaflet lipid rafts. The utility of the reporter was demonstrated in an investigation of the potential lipid raft localization of the epidermal growth factor receptor.     

Luteinizing Hormone Receptors are Confined in Mesoscale Plasma Membrane Microdomains Throughout Recovery from Receptor Desensitization

We examined the involvement of membrane microdomains during human luteinizing hormone (LH) receptor recovery from receptor desensitization after removal of bound hormone. Lateral motions of individual desensitized LH receptors expressed on the surface of Chinese hamster ovary cells and transient association of these receptors with detergent-resistant membrane (DRM) microdomains isolated using isopycnic sucrose gradient ultracentrifugation were assessed. Single particle tracking experiments showed untreated individual LH receptors to be confined within cell-surface membrane compartments with an average diameter of 199 ± 17 nm and associated with membrane fractions characteristic of bulk plasma membrane. After brief exposure to human chorionic gonadotropin (hCG), LH receptors remained for several hours desensitized to hCG challenge. Throughout this period, significantly increased numbers of LH receptors were confined within smaller diameter (<120 nm) membrane compartments and associated with DRM fragments of characteristically low density. By 5 h, when cells again produced cAMP in response to hCG, unoccupied LH receptors were found in larger 169 ± 22 nm diameter cell-surface membrane compartments and >90 % of LH receptors were again found in high-density membrane fragments characteristic of bulk plasma membrane. Taken together, these results suggest that, during recovery from LH receptor desensitization, LH receptors are both located with DRM lipid environments and confined within small, mesoscale (80–160 nm) cell-surface compartments. This may reflect hormone-driven translocation of receptors into DRM and formation there of protein aggregates too large or too rigid to permit effective signaling. Once bound hormone is removed, receptor structures would have to dissociate before receptors can again signal effectively in response to hormone challenge. Moreover, such larger protein complexes would be more easily constrained laterally by membrane structural elements and so appear resident in smaller cell-surface compartments.     

Lipid Raft-Mediated Regulation of G-Protein Coupled Receptor Signaling by Ligands which Influence Receptor Dimerization: A Computational Study

G-protein coupled receptors (GPCRs) are the largest family of cell surface receptors; they activate heterotrimeric G-proteins in response to ligand stimulation. Although many GPCRs have been shown to form homo- and/or heterodimers on the cell membrane, the purpose of this dimerization is not known. Recent research has shown that receptor dimerization may have a role in organization of receptors on the cell surface. In addition, microdomains on the cell membrane termed lipid rafts have been shown to play a role in GPCR localization. Using a combination of stochastic (Monte Carlo) and deterministic modeling, we propose a novel mechanism for lipid raft partitioning of GPCRs based on reversible dimerization of receptors and then demonstrate that such localization can affect GPCR signaling. Modeling results are consistent with a variety of experimental data indicating that lipid rafts have a role in amplification or attenuation of G-protein signaling. Thus our work suggests a new mechanism by which dimerization-inducing or inhibiting characteristics of ligands can influence GPCR signaling by controlling receptor organization on the cell membrane.     

Involvement of copper in female reproduction

Copper (Cu) is one of the essential trace metals which are necessary in maintaining the functioning of living organisms. The current knowledge on the role of copper in animal reproduction is presented in the article. Our studies have shown that complexes of copper (Cu(2+)) with gonadotropin-releasing hormone (GnRH) are even more effective in the release of LH than native GnRH. Moreover, Cu-GnRH is more potent in inducing in vivo release of FSH than LH. Copper complexes with GnRH interact with GnRH receptors (GnRHR) and modulate intracellular signaling in the gonadotrope cells of the anterior pituitary. Copper plays also a significant role in maintaining normal fetus development in mammals.