Eukaryotic translation elongation factor 1 alpha (eEF1A) inhibits Siniperca chuatsi rhabdovirus (SCRV) infection through two distinct mechanisms.

IMPORTANCE: Although a virus can regulate many cellular responses to facilitate its replication by interacting with host proteins, the host can also restrict virus infection through these interactions. In the present study, we showed that the host eukaryotic translation elongation factor 1 alpha (eEF1A), an essential protein in the translation machinery, interacted with two proteins of a fish rhabdovirus, Siniperca chuatsi rhabdovirus (SCRV), and inhibited virus infection via two different mechanisms: (i) inhibiting the formation of crucial viral protein complexes required for virus transcription and replication and (ii) promoting the ubiquitin-proteasome degradation of viral protein. We also revealed the functional regions of eEF1A that are involved in the two processes. Such a host protein inhibiting a rhabdovirus infection in two ways is rarely reported. These findings provided new information for the interactions between host and fish rhabdovirus.

Structural insights into somatostatin receptor 5 bound with cyclic peptides.

Somatostatin receptor 5 (SSTR5) is highly expressed in ACTH-secreting pituitary adenomas and is an important drug target for the treatment of Cushing's disease. Two cyclic SST analog peptides (pasireotide and octreotide) both can activate SSTR5 and SSTR2. Pasireotide is preferential binding to SSTR5 than octreotide, while octreotide is biased to SSTR2 than SSTR5. The lack of selectivity of both pasireotide and octreotide causes side effects, such as hyperglycemia, gastrointestinal disturbance, and abnormal glucose homeostasis. However, little is known about the binding and selectivity mechanisms of pasireotide and octreotide with SSTR5, limiting the development of subtype-selective SST analog drugs specifically targeting SSTR5. Here, we report two cryo-electron microscopy (cryo-EM) structures of SSTR5-Gi complexes activated by pasireotide and octreoitde at resolutions of 3.09 Å and 3.24 Å, respectively. In combination with structural analysis and functional experiments, our results reveal the molecular mechanisms of ligand recognition and receptor activation. We also demonstrate that pasireotide preferentially binds to SSTR5 through the interactions between Tyr(Bzl)/DTrp of pasireotide and SSTR5. Moreover, we find that the Q2.63, N6.55, F7.35 and ECL2 of SSTR2 play a crucial role in octreotide biased binding of SSTR2. Our results will provide structural insights and offer new opportunities for the drug discovery of better selective pharmaceuticals targeting specific SSTR subtypes.

A Halogen-Bonded Fluorescent Molecular Photoswitch: Transition from 3D Cubic Lattice to 1D Helical Superstructure for Polarization Inversion of Circularly Polarized Luminescence.

The fabrication of materials that can switch between circularly polarized luminescence (CPL) signals is both essential and challenging. Here, two new halogen-bonded fluorescent molecular photoswitches, namely, HB-switch 1 and HB-switch 2, containing α-cyano-substituted diarylethene compounds with different end groups were developed. Upon exposure to specific UV or visible light wavelengths, they exhibited controllable and reversible Z/E photoisomerization. When these switches were integrated into blue-phase liquid crystals (BPLCs), the temperature range of BP significantly expanded. Notably, the BP system incorporating HB-switch 1 exclusively achieved reversible polarization inversion of CPL signals under specific UV/visible light irradiation and during cooling/heating. The photo/thermal dual-response behavior of the CPL signals can be attributed to the phase transition from a high-symmetry 3D BP I lattice to a low-symmetry 1D helical superstructure induced by the Z/E photoisomerization of HB-switch 1 and temperature changes. This study underscores the significance of employing halogen-bond assembly strategies to design materials with switchable CPL signals, opening new possibilities for CPL-active systems.

Fusing a TurboID tag with the Andrias davidianus ranavirus 2L reduced virus adsorption efficiency.

Andrias davidianus ranavirus (ADRV) is a member of the genus ranavirus (family Iridoviridae). ADRV 2L is an envelope protein that could be essential in viral infection. In the present study, the function of ADRV 2L was investigated by fusion with the biotin ligase TurboID tag. A recombinant ADRV with a V5-TurboID tag fused in the N-terminal of 2L (ADRVT-2L) and a recombinant ADRV expressing V5-TurboID (ADRVT) were constructed, respectively. Infection of the recombinant viruses and wild-type ADRV (ADRVWT) in the Chinese giant salamander thymus cell line (GSTC) showed that ADRVT-2L had reduced cytopathic effect and lower virus titers than the other two viruses, indicating the fusion of a big tag affected ADRV infection. Analysis of the temporal expression profile showed that the expression of V5-TurboID-2L was delayed than wild-type 2L. However, electron microscopy found that the virion morphogenesis was not affected in ADRVT-2L-infected cells. Furthermore, the virus binding assay revealed that the adsorption efficiency of ADRVT-2L was considerably decreased compared to the other two viruses. Therefore, these data showed that linking the TurboID tag to ADRV 2L affected virus adsorption to the cell membrane, which suggested an important role of 2L in virus entry into cells.

Thiazolo[5,4-d]thiazole-Based Metal-Organic Framework for Catalytic CO2 Cycloaddition and Photocatalytic Benzylamine Coupling Reactions.

Metal-organic frameworks (MOFs) with permanent porosity and multifunctional catalytic sites constructed by two or more organic ligands are regarded as effective heterogeneous catalysts to improve certain organic catalytic reactions. In this work, a pillared-layer Zn-MOF (MOF-LS10) was constructed by 2,3,5,6-tetrakis(4-carboxyphenyl)pyrazine (H4TCPP) and 2,5-di(pyridin-4-yl)thiazolo[5,4-d]thiazole (DPTZTZ). After activation, MOF-LS10 has a permanent porosity and moderate CO2 adsorption capacity. The introduction of thiazolo[5,4-d]thiazole (TZTZ), a photoactive unit, into the framework endows MOF-LS10 with excellent photocatalytic performance. MOF-LS10 can not only efficiently catalyze the formation of cyclic carbonates from CO2 and epoxide substrates under mild conditions but also can photocatalyze benzylamine coupling at room temperature. In addition, we used another two ligands 1,2,4,5-tetrakis(4-carboxyphenyl)benzene (H4BTEB) and 1,4-di(pyridin-4-yl)benzene (DPB) to synthesize MOF-LS11 (constructed by BTEB4- and DPTZTZ) and MOF-LS12 (constructed by TCPP4- and DPB) in order to explore whether the pyrazine structural unit and the TZTZ structural unit synergistically catalyze the reaction. The electron paramagnetic resonance spectrum demonstrates that the superoxide radical (·O2-), generated by electron transfer from the MOF excited by light to the oxidant, is the main active substance of oxidation. The design and synthesis of MOF-LS10 provide an effective synthetic strategy for the development of versatile heterogeneous catalysts for various organic reactions and a wide range of substrates.

A Photo- and Thermo-Driven Azoarene-Based Circularly Polarized Luminescence Molecular Switch in a Liquid Crystal Host.

The development of chiral optical active materials with switchable circularly polarized luminescence (CPL) signals remains a challenge. Here an azoarene-based circularly polarized luminescence molecular switch, (S, R, S)-switch 1 and (R, R, R)-switch 2, are designed and prepared with an (R)-binaphthyl azo group as a chiral photosensitive moiety and two (S)- or (R)-binaphthyl fluorescent molecules with opposite or the same handedness as chiral fluorescent moieties. Both switches exhibit reversible trans/cis isomerization when irradiated by 365 nm UV light and 520 nm green light in solvent and liquid crystal (LC) media. In contrast with the control (R, R, R)-switch 2, when switch 1 is doped into nematic LCs, polarization inversion and switching-off of the CPL signals are achieved in the resultant helical superstructure upon irradiation with 365 nm UV and 520 nm green light, respectively. Meanwhile, the fluorescence intensity of the system is basically unchanged during this switching process. In particular, these variations of the CPL signals could be recovered after heating, realizing the true sense of CPL reversible switching. Taking advantage of the unique CPL switching, the proof-of-concept for "a dual-optical information encryption system" based on the above CPL active material is demonstrated.

Development and characterization of a skin cell line from Chinese perch (Siniperca chuatsi) and its application in aquatic animal viruses.

Chinese perch (Siniperca chuatsi), an important fish for the aquaculture industry of China, is often affected by viral diseases. A stable and sensitive cell line can play an important role in virus identification and isolation, functional gene identification, virus pathogenic mechanism and antiviral immunity study. In the present study, a new cell line (S. chuatsi skin cell, SCSC) derived from the skin of S. chuatsi was established. The SCSC mainly consisted of fibroblastic-like cells, which grew well in M199 medium supplemented with 10% foetal bovine serum at 25°C. Chromosome analysis revealed that the SCSC (44%) has a diploid chromosome number of 2n = 48. The SCSC can be transfected and expressed exogenous gene efficiently. It also showed high sensitivity to several aquatic animal viruses from different families including Rhabdoviridae, Iridoviridae and Reoviridae. In addition, RT-PCR showed that S. chuatsi rhabdovirus (SCRV) started genome replication as early as 3 h post infection in the cells, which also induced the up-regulation of a variety of immune-related genes including these related to interleukin family, pattern recognition receptors, JAK-STAT pathway and interferon regulatory factors. In summary, current study provided a new tool in research of fish viruses and its interaction with host.

Molecular Expansion for Constructing Porous Organic Polymers with High Surface Areas and Well-Defined Nanopores.

Construction of porous organic polymers (POPs) with high surface areas, well-defined nanopores, and excellent stability remains extremely challenging because of the unmanageable reaction process. Until now, only a few reported POPs have Brunauer-Emmett-Teller (BET) surface areas (SBET ) exceeding 3000 m2 g-1 . Herein, we demonstrate a molecular expansion strategy to integrate high surface areas, large nanopore sizes, and outstanding stability into POPs. A series of hyper-crosslinked conjugated polymers (HCCPs) with exceptional porosity are synthesized through this strategy. Specially, HCCP-6 and HCCP-11 exhibit the highest surface areas (SBET >3000 m2 g-1 ) and excellent total pore volumes (up to 3.98 cm3 g-1 ) among these HCCPs. They present decent total CH4 storage capacities of 491 and 421 mg g-1 at 80 bar and 298 K, respectively. Meanwhile, they are highly stable in harsh environments. The facile and general molecular expansion strategy would lead to improved synthetic routes of POPs for desired functions.

Arsenic(V) reduction in relation to Iron(III) transformation and molecular characterization of the structural and functional microbial community in sediments of a basin-fill aquifer in Northern Utah.

Basin-fill aquifers of the Southwestern United States are associated with elevated concentrations of arsenic (As) in groundwater. Many private domestic wells in the Cache Valley Basin, UT, have As concentrations in excess of the U.S. EPA drinking water limit. Thirteen sediment cores were collected from the center of the valley at the depth of the shallow groundwater and were sectioned into layers based on redoxmorphic features. Three of the layers, two from redox transition zones and one from a depletion zone, were used to establish microcosms. Microcosms were treated with groundwater (GW) or groundwater plus glucose (GW+G) to investigate the extent of As reduction in relation to iron (Fe) transformation and characterize the microbial community structure and function by sequencing 16S rRNA and arsenate dissimilatory reductase (arrA) genes. Under the carbon-limited conditions of the GW treatment, As reduction was independent of Fe reduction, despite the abundance of sequences related to Geobacter and Shewanella, genera that include a variety of dissimilatory iron-reducing bacteria. The addition of glucose, an electron donor and carbon source, caused substantial shifts toward domination of the bacterial community by Clostridium-related organisms, and As reduction was correlated with Fe reduction for the sediments from the redox transition zone. The arrA gene sequencing from microcosms at day 54 of incubation showed the presence of 14 unique phylotypes, none of which were related to any previously described arrA gene sequence, suggesting a unique community of dissimilatory arsenate-respiring bacteria in the Cache Valley Basin.

Study of the cement implantation syndrome: A review.

Bone cement implantation syndrome (BCIS) is a critical and potentially life-threatening condition that manifests during implantation. Characterized by a constellation of symptoms, including hypoxemia, hypotension, cardiac arrhythmias, elevated pulmonary vascular resistance, and occasionally cardiac arrest, BCIS typically ensues shortly after cement introduction, albeit with rare instances of delayed onset. Primarily attributed to the exothermic reaction of bone cement implantation, this syndrome is caused by local tissue damage, histamine and prostaglandin release, and microemboli formation, ultimately triggering a systemic immune response that culminates in respiratory and circulatory failure. The current hypotheses regarding BCIS include embolism, allergic reactions, and cement autotoxicity. BCIS management emphasizes preventative strategies, encompassing meticulous patient risk assessment, comprehensive preoperative and intraoperative evaluations, and precise cement application techniques. Treatment primarily involves symptomatic therapy and life-support measures to address the systemic effects of the syndrome.

The Role of Macrophages in Nerve Regeneration: Polarization and Combination with Tissue Engineering.

Peripheral nerve regeneration after trauma poses a substantial clinical challenge that has already been investigated for many years. Infiltration of immune cells is a critical step in the response to nerve damage that creates a supportive microenvironment for regeneration. In this work, we focus on a special type of immune cell, macrophage, in addressing the problem of neuronal regeneration. We discuss the complex endogenous mechanisms of peripheral nerve injury and regrowth vis-à-vis macrophages, including their recruitment, polarization, and interplay with Schwann cells post-trauma. Furthermore, we elucidate the underlying mechanisms by which exogenous stimuli govern the above events. Finally, we summarize the necessary roles of macrophages in peripheral nerve lesions and reconstruction. There are many challenges in controlling macrophage functions to achieve complete neuronal regeneration, even though considerable progress has been made in understanding the connection between these cells and peripheral nerve damage.

Recent Advances in Smart Windows Based on Photo-Responsive Liquid Crystals Featuring Phase Transition.

A smart window is an optical dimming device with intelligent functions that can control its relevant performances through external stimuli, achieving functions such as privacy protection and temperature regulation. Light is an ideal stimulus for regulating smart windows, which is noninvasive and allows self-adaptable manipulation of materials. This review highlights recent significant achievements in smart windows constructed by photo-responsive liquid crystals (LCs) systems that can undergo the transition between different phases. The smart windows based on photo-responsive LCs are used in a plethora of areas, including privacy protection, absorption glass, building decoration, energy saving, and climate modulation applications. The review concludes with a brief perspective on some significant challenges and opportunities for the future development of photo-responsive smart windows, which is crucial for expanding the applications of smart windows and improving their performances.

S-glutathionylation of the Na,K-ATPase catalytic α subunit is a determinant of the enzyme redox sensitivity.

Na,K-ATPase is highly sensitive to changes in the redox state, and yet the mechanisms of its redox sensitivity remain unclear. We have explored the possible involvement of S-glutathionylation of the catalytic α subunit in redox-induced responses. For the first time, the presence of S-glutathionylated cysteine residues was shown in the α subunit in duck salt glands, rabbit kidneys, and rat myocardium. Exposure of the Na,K-ATPase to oxidized glutathione (GSSG) resulted in an increase in the number of S-glutathionylated cysteine residues. Increase in S-glutathionylation was associated with dose- and time-dependent suppression of the enzyme function up to its complete inhibition. The enzyme inhibition concurred with S-glutathionylation of the Cys-454, -458, -459, and -244. Upon binding of glutathione to these cysteines, the enzyme was unable to interact with adenine nucleotides. Inhibition of the Na,K-ATPase by GSSG did not occur in the presence of ATP at concentrations above 0.5 mm. Deglutathionylation of the α subunit catalyzed by glutaredoxin or dithiothreitol resulted in restoration of the Na,K-ATPase activity. Oxidation of regulatory cysteines made them inaccessible for glutathionylation but had no profound effect on the enzyme activity. Regulatory S-glutathionylation of the α subunit was induced in rat myocardium in response to hypoxia and was associated with oxidative stress and ATP depletion. S-Glutathionylation was followed by suppression of the Na,K-ATPase activity. The rat α2 isoform was more sensitive to GSSG than the α1 isoform. Our findings imply that regulatory S-glutathionylation of the catalytic subunit plays a key role in the redox-induced regulation of Na,K-ATPase activity.

Bidirectional potential effects of DON transformation in vadose zones on groundwater nitrate contamination: Different contributions to nitrification and denitrification.

The main cause of groundwater nitrate contamination is the continual downward migration of dissolved nitrogen (N) in vadose zone with leachate. In recent years it has been found that dissolved organic N (DON) rise to forefront due to its great migration capacity and environmental effects. However, it remains unknown how the transformation behaviors of DONs with different properties in vadose zone profile may impact N forms distribution and groundwater nitrate contamination. To address the issue, we conducted a series of 60-day microcosm incubation experiments to investigate the effects of various DONs transformation behaviors on the distribution of N forms, microbial communities, and functional genes. The results revealed that urea and amino acids mineralized immediately after substrates addition. By contrast, amino sugars and proteins caused less dissolved N throughout entire incubation period. The transformation behaviors could substantially alter the microbial communities. Moreover, we discovered that amino sugars remarkably increased the absolute abundances of denitrification function genes. These results delineated that DONs with unique characteristics (such as amino sugar) promoted different N geochemical processes in distinct ways: different contributions to nitrification and denitrification. This can provide new insights for nitrate non-point source pollution control in groundwater.

Dual-Shell Microcapsules for High-Response Efficiency Self-Healing of Multi-Scale Damage in Waterborne Polymer-Cement Coatings.

Waterborne polymer-cement coatings have been widely applied in building materials due to their organic solvent-free nature, low cost, and eco-friendliness. However, these coatings can easily crack during the drying process as a result of construction environment factors, compromising the barrier performance of the coating and limiting its large-scale application. In this study, a dual-shell self-healing microcapsule was developed, which can effectively heal damage on a macro scale in waterborne polymer-cement coatings. Specifically, this dual-shell self-healing microcapsule was designed with a silica gel shell and a tannic acid-cuprum (TA-Cu) double-shell structure embedded with an epoxy resin (EP) healing agent, which was successfully fabricated via a two-step in situ polymerization. This silica gel shell self-healing microcapsules can effectively load into waterborne polymer-cement coatings. As the coating dries and solidifies, the silica gel shell of the microcapsule also becomes loose and brittle due to dehydration. This improves the mechanical initiation efficiency of the microcapsules in the coating. This study provides a novel approach for the application of self-healing microcapsules in waterborne coating systems, which can significantly reduce cracking during the drying process of waterborne polymer-cement coatings and improve the service life of the coating under complex conditions.

Siniperca chuatsi Rhabdovirus (SCRV)-Induced Key Pathways and Major Antiviral Genes in Fish Cells.

Fish rhabdoviruses, including Siniperca chuatsi rhabdovirus (SCRV), are epidemic pathogens that harm fish aquaculture. To clarify the interactions between SCRV and its host and explore antiviral targets, the present study performed transcriptome analysis in a cultured S. chuatsi skin cell line (SCSC) after SCRV infection at 3, 12, 24, and 36 h post-infection (hpi). Comparison with control obtained 38, 353, 896, and 1452 differentially expressed genes (DEGs) in the detected time points, respectively. Further analysis of the Go terms and KEGG pathways revealed the key pathways "Cytokine-cytokine receptor interaction" and "interferon related pathways" in SCSC cells responding to SCRV infection. The significantly up-regulated genes in the pathways were also verified by qPCR. Furthermore, gene cloning and overexpression revealed that five interferon-stimulated genes (ISGs) IFI4407, IFI35, Viperin, IFIT1, and IFIT5 had the ability to inhibit SCRV replication in FHM (Fathead minnow) cells, especially an inhibition efficiency more than 50% was observed in IFI35 overexpressed cells. In summary, current study revealed the main innate immune pathways in S. chuatsi cells induced by SCRV infection and the major ISGs of S. chuatsi in controlling SCRV replication.

Post-crosslinking of conjugated microporous polymers using vinyl polyhedral oligomeric silsesquioxane for enhancing surface areas and organic micropollutants removal performance from water.

High-capacity and rapid adsorption of organic micropollutants (OMPs) from water by adsorbents remain a great significance in water treatment. Recently, porous organic polymers with high surface areas, tunable nanopores and easy-to-modify skeletons are promising new generation of adsorbents. Here, a series of silsesquioxane-crosslinked conjugated microporous polymers (PcCMPs) with high surface areas and well-defined nanopores are developed via a molecular expansion strategy for removing OMPs from water. Among these PcCMPs, PcCMP-2E exhibited the highest Brunauer-Emmett-Teller surface area up to 2518 m2 g-1. The maximum adsorption capacities of bisphenol A (BPA) of PcCMPs are ranging from 485.44 to 628.93 mg g-1. Specially, >93.5% of BPA could be removed even through a thin layer filtration device composed of PcCMPs, which can be regenerated well using a mild washing procedure. PcCMPs also exhibit extraordinary adsorption to a variety of OMPs, such as tetracycline (226.99 mg g-1), 1-naphthylamine (290.07 mg g-1), 2-naphthol (213.87 mg g-1), 2,4-dichlorophenol (183.85 mg g-1) and p-nitrophenol (360.24 mg g-1). This work provides a new strategy to design porous adsorbents with high adsorption capacity and fast adsorption rate for water treatment.

Evaluation of Mutton Quality Characteristics of Dongxiang Tribute Sheep Based on Membership Function and Gas Chromatography and Ion Mobility Spectrometry.

Dongxiang tribute sheep have a history of use in food dishes such as "Dongxiang Handgrip," which dates back hundreds of years and is a favorite halal food in northwestern China. However, little is known about the mutton quality characteristics of Dongxiang tribute sheep. Here, we measured the sensory characteristics, nutritional quality, and flavor substances to comprehensively evaluate the mutton quality characteristics of these sheep. The mutton qualities of Dongxiang tribute, Tibetan, Ujumqin, and Hu sheep were comprehensively evaluated by membership function. Subsequently, the volatile components in mutton samples from 30 Dongxiang tribute sheep were detected via gas chromatography and ion mobility spectrometry (GC-IMS), and their fingerprints were established. The result of meat quality revealed that the shear force, the contents of protein, essential amino acid (EAA), non-essential amino acid (NEAA), and n-6/n-3 ratio of Dongxiang tribute mutton were better than the other three breeds. Membership functions were calculated for 10 physical and chemical indexes of mutton quality, and the comprehensive membership function values of the four breeds in order of highest to lowest mutton quality were Tibetan sheep (0.76) > Dongxiang tribute sheep (0.49) > Hu sheep (0.46) > Ujumqin sheep (0.33). Thirty volatile compounds were identified via GC-IMS: seven alcohols, eight aldehydes, five ketones, two esters, two phenols, one ether, one furan, one acid, two hydrocarbons, and one pyrazine. Ketones, aldehydes, and alcohols were the main volatile compounds forming the flavor of Dongxiang tribute sheep mutton. The reliability of the results was validated by PCA (principal component analysis) and similarity analyses. Our results provide reference value for consumers of mutton in China.

Improvement, Validation, and Analysis of Colles Fracture Treated with an Integrated Retainer Pad Splint.

Objective: To observe the effectiveness and safety of the Colles fracture treated with the integrated retainer pad splint and to compare the clinical and radiological outcomes of the integrated retainer pad splint and the traditional bamboo curtain splint in the treatment of the Colles fracture. Methods: A total of 100 patients with Colles fractures were randomly divided into two groups: the treatment group was fixed with the integrated retainer pad splint (IS), and the control group was fixed with the traditional bamboo curtain splint (TS).The range of wrist motion was measured at follow-up examinations, and volar inclination, ulnar deviation, and radial height were measured on radiographs. Regular follow-up wrist imaging examinations and functional examinations were performed before reduction, after reduction, and at the 1st, 3rd, 5th, and 8th weeks. The two groups were compared in terms of convenience, fracture healing time, X-ray data of volar inclination, ulnar deviation, radial height, and wrist joint function. The relevant data were analyzed with SPSS 25.0 statistical software. Results: There were no notable differences in gender, age, and injured side between IS and TS groups. In terms of operation time, IS was better than the TS group (P < 0.05), and the operation time in the IS group was shorter. On the basis of X-ray data of volar inclination, ulnar deviation, and radial height measured on radiographs, the difference between the IS and TS groups was statistically significant (P < 0.05), which showed that the IS group was more stable in fracture fixation and had less reduction loss during the treatment process. At the 8th week of treatment, the wrist Gartland-Werley score of the two groups showed that the two fixation methods are equivalent in restoring wrist joint function (P > 0.05); however, in terms of the excellent and good rate of wrist joint function, the IS group scored 96% was higher than the TS group (80%). Conclusion: Compared with the traditional bamboo curtain splint, the integrated retainer pad splint is more convenient and stable, and it has less reduction loss during the treatment. Repair of the Colles fracture using the integrated retainer pad splint with external fixation results in nearly normal return of function, which is significantly better than using the traditional bamboo curtain splint.

Structural insights into the activation of somatostatin receptor 2 by cyclic SST analogues.

The endogenous cyclic tetradecapeptide SST14 was reported to stimulate all five somatostatin receptors (SSTR1-5) for hormone release, neurotransmission, cell growth arrest and cancer suppression. Two SST14-derived short cyclic SST analogues (lanreotide or octreotide) with improved stability and longer lifetime were developed as drugs to preferentially activate SSTR2 and treat acromegalia and neuroendocrine tumors. Here, cryo-EM structures of the human SSTR2-Gi complex bound with SST14, octreotide or lanreotide were determined at resolutions of 2.85 Å, 2.97 Å, and 2.87 Å, respectively. Structural and functional analysis revealed that interactions between ß-turn residues in SST analogues and transmembrane SSTR2 residues in the ligand-binding pocket are crucial for receptor binding and functional stimulation of the two SST14-derived cyclic octapeptides. Additionally, Q1022.63, N2766.55, and F2947.35 could be responsible for the selectivity of lanreotide or octreotide for SSTR2 over SSTR1 or SSTR4. These results provide valuable insights into further rational development of SST analogue drugs targeting SSTR2.