Glutamate is the major excitatory neurotransmitter in the mammalian central nervous system (CNS). Packaging and storage of glutamate into glutamatergic neuronal vesicles require ATP-dependent vesicular glutamate uptak...Glutamate is the major excitatory neurotransmitter in the mammalian central nervous system (CNS). Packaging and storage of glutamate into glutamatergic neuronal vesicles require ATP-dependent vesicular glutamate uptake systems, which utilize the electrochemical proton gradient as a driving force. Three vesicular glutamate transporters (VGLUT1-3) have been recently identified from neuronal tissue where they play a key role to maintain the vesicular glutamate level. Recently, it has been demonstrated that glutamate signaling is also functional in peripheral neuronal and non-neuronal tissues, and occurs in sites of pituitary, adrenal, pineal glands, bone, GI tract, pancreas,skin, and testis. The glutamate receptors and VGLUTs in digestivesystem have been found in both neuronal and endocrinal cells. The glutamate signaling in the digestive system may have significant relevance to diabetes and GI tract motility disorders. This review will focus on the most recent update of molecular physiology of digestive VGLUTs.展开更多
Objective Aims to delineate the distribution profile of three isoforms of vesicular glutamate transporter （VGluT）, viz. VGluT1-3, and their cellular localization within vestibular nuclear complex （VNC）. Methods Br...Objective Aims to delineate the distribution profile of three isoforms of vesicular glutamate transporter （VGluT）, viz. VGluT1-3, and their cellular localization within vestibular nuclear complex （VNC）. Methods Brain sections from normal Sprague-Dawley rats were processed immunohistochemically for VGluT detection, employing avidinbiotinylated peroxidase complex method with 3-3＇-diaminobenzidine （DAB） as chromogen. Results The whole VNC expressed all of the three transporters that were observed to be localized to the fiber endings. Compared with VGluT1 and VGluT3, VGluT2 demonstrated a relatively homogeneous distribution, with much higher density in VNC. VGluT3 displayed the highest density in lateral vestibular nucleus and group X, contrasting with the sparse immunostained puncta within vestibular medial and inferior nuclei. Conclusion Glutamtatergic pathways participate in the processing of vestibular signals within VNC mainly through the re-uptake of glutamate into synaptic vesicles by VGluT1 and 2, whereas VGluT3 may play a similar role mainly in areas other than medial and inferior nuclei of VNC.展开更多
Objective:To study the antitoxic role of vesicular monoamine transporter 2 (VMAT2) in transpgenic Chinese Hamster ovary(CHO) cell.Methods:With the technology of transgene from PC12 to CHO,MTT reduction assay was used ...Objective:To study the antitoxic role of vesicular monoamine transporter 2 (VMAT2) in transpgenic Chinese Hamster ovary(CHO) cell.Methods:With the technology of transgene from PC12 to CHO,MTT reduction assay was used to detect MPP^+ toxic effect on wild type CHO(wtCHO) and transgenic CHO.Meanwhile,the role of reserpine was also observed in MPP^+ toxic effects.Results:The sensitivity of transgenic CHO to MPP^+ was much less than that of wtCHO with 0.5 mmol/L MPP^+.Transgenic CHO had the same sensitivity as wtCHO if rotenone was given.WtCHO,by given reserpine alone,didn''''''''t change its sensitivity to MPP^+.Conclusions:VMAT2 has protective effect on transgenic CHO by transporting MPP^+ to vesicles.展开更多
The processes of mitochondrial restitution are controlled by nuclear genes that encode proteins synthesized in ER and cytosol and delivered as organelle- and membrane-specific transport vesicles. The analysis of the t...The processes of mitochondrial restitution are controlled by nuclear genes that encode proteins synthesized in ER and cytosol and delivered as organelle- and membrane-specific transport vesicles. The analysis of the transporters recovered from inner mitochondrial space (Mitosol) revealed that the ER-synthesized mitochondria-specific transport vesicles consist of two carriers, one remaining in outer mitochondrial membrane (OMM), and the other that transfers specific membrane segments to the inner mitochondrial membrane (IMM). The ER-assembled and IMM-committed membrane segments, while first integrated into OMM, undergo intra-mitochondrial lipid modification reflected in the synthesis of cardiolipin (CL) and inversion into Mitosol with load of IMM associated cytosolic proteins. Then, the CL-bedecked vesicles are released from OMM to Mitosol and upon contact with IMM fuse with the membrane, and the release of cytosolic cargo ensues. While ER-assembled mitochondria-specific transport vesicles fuse with OMM with the aid of the cytosolic, phosphatidylglycerol (PG)-specific phospholipase A2 (PLA2), the Mitosol-contained CL-specific PLA guides vesicles fusion with IMM. The described path of translocation of the membrane segments and the cytosol synthesized proteins into the designated mitochondrial compartments sustains growth and identity of OMM, IMM, maintains protein delivery for intra-mitochondrial lipid and protein modification in Mitosol, and ensures conformity of the cytosolic proteins cargo delivered to matrix.展开更多
The human body consists of several physiological barriers that express a number of membrane transporters. For an orally absorbed drug the intestinal, hepatic, renal and blood-brain barriers are of the greatest importa...The human body consists of several physiological barriers that express a number of membrane transporters. For an orally absorbed drug the intestinal, hepatic, renal and blood-brain barriers are of the greatest importance. The ATP-binding cassette(ABC) transporters that mediate cellular efflux and the solute carrier transporters that mostly mediate cellular uptake are the two superfamilies responsible for membrane transport of vast majority of drugs and drug metabolites. The total number of human transporters in the two superfamilies exceeds 400, and about 40-50 transporters have been characterized for drug transport. The latest Food and Drug Administration guidance focuses on P-glycoprotein, breast cancer resistance protein, organic anion transporting polypeptide 1B1(OATP1B1), OATP1B3, organic cation transporter 2(OCT2), and organic anion transporters 1(OAT1) and OAT3. The European Medicines Agency's shortlist additionally contains the bile salt export pump, OCT1, and the multidrug and toxin extrusion transporters, multidrug and toxin ex-trusion protein 1(MATE1) and MATE2/MATE2 K. A variety of transporter assays are available to test drugtransporter interactions, transporter-mediated drugdrug interactions, and transporter-mediated toxicity. The drug binding site of ABC transporters is accessible from the cytoplasm or the inner leaflet of the plasma membrane. Therefore, vesicular transport assays utilizing inside-out vesicles are commonly used assays, where the directionality of transport results in drugs being transported into the vesicle. Monolayer assays utilizing polarized cells expressing efflux transporters are the test systems suggested by regulatory agencies. However, in some monolayers, uptake transporters must be coexpressed with efflux transporters to assure detectable transport of low passive permeability drugs. For uptake transporters mediating cellular drug uptake, utilization of stable transfectants have been suggested. In vivo animal models complete the testing battery. Some issues, such as in vivo relevance, gender difference, age and ontogeny issues can only be addressed using in vivo models. Transporter specificity is provided by using knock-out or mutant models. Alternatively, chemical knock-outs can be employed. Compensatory changes are less likely when using chemical knockouts. On the other hand, specific inhibitors for some uptake transporters are not available, limiting the options to genetic knock-outs.展开更多
Vesicle-based traffi cking of hepatocellular transporters involves delivery of the newly-synthesized carriers from the rough endoplasmic reticulum to either the plasma membrane domain or to an endosomal,submembrane co...Vesicle-based traffi cking of hepatocellular transporters involves delivery of the newly-synthesized carriers from the rough endoplasmic reticulum to either the plasma membrane domain or to an endosomal,submembrane compartment,followed by exocytic targeting to the plasma membrane. Once delivered to the plasma membrane,the transporters usually undergo recycling between the plasma membrane and the endosomal compartment,which usually serves as a reservoir of pre-existing transporters available on demand. The balance between exocytic targeting and endocytic internalization from/to this recycling compartment is therefore a chief determinant of the overall capability of the liver epithelium to secrete bile and to detoxify endo and xenobiotics. Hence,it is a highly regulated process. Impaired regulation of this balance may lead to abnormal localization of these transporters,which results in bile secretory failure due to endocytic internalization of key transporters involved in bile formation. This occurs in several experimental models of hepatocellular cholestasis,and in most human cholestatic liver diseases. This review describes the molecular bases involved in the biology of the dynamic localization of hepatocellular transporters and its regulation,with a focus on the involvement of signaling pathways in this process. Their alterations in different experimental models of cholestasis and in human cholestatic liver disease are reviewed. In addition,the causes explaining the pathological condition (e.g. disorganization of actin or actin-transporter linkers) and the mediators involved (e.g. activation of cholestatic signaling transduction pathways) are also discussed. Finally,several experimental therapeutic approaches based upon the administration of compounds known to stimulate exocytic insertion of canalicular transporters (e.g. cAMP,tauroursodeoxycholate) are described.展开更多
The synthesis of endoplasmic reticulum (ER)-derived transport vesicles is dictated by the contents and derivation of the cellular cytosol. The ER transport vesicles synthesized in the presence of gastric epithelial ce...The synthesis of endoplasmic reticulum (ER)-derived transport vesicles is dictated by the contents and derivation of the cellular cytosol. The ER transport vesicles synthesized in the presence of gastric epithelial cells cytosol are destined for en bloc fusion with apical epithelial membrane, whereas those generated in hepa-tocytes-derived cytosol are destined for en bloc fusion with basolateral membrane. Moreover, during assembly of the dominant fraction of the apical or basolateral transport vesicles, a sub-stantial fraction of the vesicles is produced that fuses with endosomes, and the vesicles with still unknown destination that remain in cytosol. The process of ER vesicles synthesis is blocked by RNase treatment, whereas Golgi vesicles as-sembly is not affected. The experiments indicate that transport vesicles’ membrane composition and fidelity of its construction is defined in ER. The process involves synchronous membrane lipid synthesis, cotranslational intercalation of integral membrane proteins and containment of the vesicular cargo.展开更多
Hrr25是酿酒酵母中Ⅰ型酪蛋白激酶家族成员,具有丝氨酸/苏氨酸蛋白激酶活性。其可以通过磷酸化多种蛋白质来发挥作用。Hrr25的底物蛋白质包括自噬相关蛋白、COPⅡ(coat protein complexes Ⅱ)囊泡衣被蛋白Sec24和Sec23、真核翻译起始因...Hrr25是酿酒酵母中Ⅰ型酪蛋白激酶家族成员,具有丝氨酸/苏氨酸蛋白激酶活性。其可以通过磷酸化多种蛋白质来发挥作用。Hrr25的底物蛋白质包括自噬相关蛋白、COPⅡ(coat protein complexes Ⅱ)囊泡衣被蛋白Sec24和Sec23、真核翻译起始因子6、γ-微管蛋白Tub4、延长器复合蛋白1等。另外Hrr25还可以与减数分裂重组蛋白Rec8、核孔蛋白Nup53、转录调节因子Crz1、转录激活因子Haa1等相互作用。Hrr25的多种相互作用蛋白质使其在自噬、囊泡运输、微管组装、减数分裂、有丝分裂、DNA修复、核糖体生物发生和弱有机酸胁迫途径等多种生物过程发挥作用。为了更好地了解Hrr25在各个生物过程中的作用机制以及各个生物过程之间的联系,本文总结了Hrr25的生物学功能及其作用机制,并概述其研究的潜在意义,为Hrr25的进一步研究提供理论依据。展开更多
The endosomal trafficking of signaling membrane proteins, such as receptors, transporters and channels, is mediated by the retromer-mediated sorting machinery, composed of a cargo-selective vacuolar protein sorting tr...The endosomal trafficking of signaling membrane proteins, such as receptors, transporters and channels, is mediated by the retromer-mediated sorting machinery, composed of a cargo-selective vacuolar protein sorting trimer and a membrane-deforming subunit of sorting nexin proteins. Recent studies have shown that the isoforms, sorting nexin 5 (SNX5) and SNX6, have played distinctive regulatory roles in retrograde membrane trafficking. However, the molecular insight determined functional differences within the proteins remains unclear. We reported that SNX5 and SNX6 had distinct binding affinity to the cargo protein vesicular monoamine transporter 2 (VMAT2). SNX5, but not SNX6, specifically interacted with VMAT2 through the Phox domain, which contains an alpha-helix binding motif. Using chimeric mutagenesis, we identified that several key residues within this domain were unique in SNX5, but not SNX6, and played an auxiliary role in its binding to VMAT2. Importantly, we generated a set of mutant SNX6, in which the corresponding key residues were mutated to those in SNX5. In addition to the gain in binding affinity to VMAT2, their overexpression functionally rescued the altered retrograde trafficking of VMAT2 induced by siRNA-mediated depletion of SNX5. These data strongly suggest that SNX5 and SNX6 have different functions in retrograde membrane trafficking, which is determined by the different structural elements within the Phox domain of two proteins. Our work provides a new information on the role of SNX5 and SNX6 in the molecular regulation of retrograde membrane trafficking and vesicular membrane targeting in monoamine neurotransmission and neurological diseases.展开更多
目的观察慢性束缚应激后,小鼠清醒状态下咬肌肌电水平以及支配咬肌运动的三叉神经运动核(trigeminal motor nucleus,Vmo)神经元的变化,为探究心理因素与颞下颌关节紊乱病发生的相关中枢调控机制提供实验依据。方法32只雄性小鼠被随机分...目的观察慢性束缚应激后,小鼠清醒状态下咬肌肌电水平以及支配咬肌运动的三叉神经运动核(trigeminal motor nucleus,Vmo)神经元的变化,为探究心理因素与颞下颌关节紊乱病发生的相关中枢调控机制提供实验依据。方法32只雄性小鼠被随机分为对照组、应激组,对应激组小鼠施加4 h/d、连续14 d的慢性束缚应激;对照组小鼠正常饲养。14 d后,通过旷场实验与高架十字迷宫实验观察小鼠的行为学改变;检测清醒状态下小鼠咬肌肌电水平;采用全细胞膜片钳技术观察Vmo神经元的电生理特性,并利用免疫组织荧光技术观察Vmo内Ⅰ型、Ⅱ型囊泡膜谷氨酸转运体(vesicular glutamate transporter 1/2,VGLUT1/2)的表达情况。结果应激组小鼠在旷场实验的中央活动时间(P=0.0004)与中央活动路程(P=0.0004)均显著低于对照组;高架十字迷宫实验中应激组小鼠的开臂进入次数百分比(P=0.0002)与滞留开臂时间百分比(P=0.0013)均显著低于对照组,显示存在明显的焦虑样行为。对照组和应激组小鼠在应激开始前,咬肌累积肌电(integral electromyography,iEMG)(P=0.8779)及振幅均方根(root mean square,RMS)(P>0.9999)均无明显差异;应激结束后,应激组小鼠咬肌的iEMG(P=0.0004)和RMS值(P=0.0001)均显著高于对照组。对照组小鼠在应激前后的iEMG(P=0.7989)和RMS值(P>0.9999)比较无显著差异;应激组小鼠在应激结束后,其咬肌的iEMG(P=0.0011)和RMS值(P=0.0019)显著高于应激前水平。电生理结果显示,在电流钳模式下,当输入60、80、100 pA电流时,应激组小鼠Vmo神经元的放电频率显著高于对照组(P<0.05);应激组小鼠Vmo神经元的自发性兴奋性突触后电流频率(P=0.0030)与幅度(P=0.0002)显著高于对照组。免疫组织荧光染色结果显示,应激组小鼠Vmo部位的VGLUT1(P=0.0010)与VGLUT2荧光强度(P=0.0013)均显著高于对照组。结论慢性束缚应激能够导致小鼠的焦虑样行为及咬肌肌电活动水平的增高。应激后脑内Vmo神经元兴奋性升高,其受到的谷氨酸能兴奋性投射增多,可能是束缚应激造成咬肌肌电活动水平升高的中枢机制之一。展开更多
基金Supported by the National Institute of Diabetes and Digestive Kidney Diseases Grant R01-DK063142 and R01-DK33209
文摘Glutamate is the major excitatory neurotransmitter in the mammalian central nervous system (CNS). Packaging and storage of glutamate into glutamatergic neuronal vesicles require ATP-dependent vesicular glutamate uptake systems, which utilize the electrochemical proton gradient as a driving force. Three vesicular glutamate transporters (VGLUT1-3) have been recently identified from neuronal tissue where they play a key role to maintain the vesicular glutamate level. Recently, it has been demonstrated that glutamate signaling is also functional in peripheral neuronal and non-neuronal tissues, and occurs in sites of pituitary, adrenal, pineal glands, bone, GI tract, pancreas,skin, and testis. The glutamate receptors and VGLUTs in digestivesystem have been found in both neuronal and endocrinal cells. The glutamate signaling in the digestive system may have significant relevance to diabetes and GI tract motility disorders. This review will focus on the most recent update of molecular physiology of digestive VGLUTs.
基金National Natural Science Foundation of China （No. 30470562）.
文摘Objective Aims to delineate the distribution profile of three isoforms of vesicular glutamate transporter （VGluT）, viz. VGluT1-3, and their cellular localization within vestibular nuclear complex （VNC）. Methods Brain sections from normal Sprague-Dawley rats were processed immunohistochemically for VGluT detection, employing avidinbiotinylated peroxidase complex method with 3-3＇-diaminobenzidine （DAB） as chromogen. Results The whole VNC expressed all of the three transporters that were observed to be localized to the fiber endings. Compared with VGluT1 and VGluT3, VGluT2 demonstrated a relatively homogeneous distribution, with much higher density in VNC. VGluT3 displayed the highest density in lateral vestibular nucleus and group X, contrasting with the sparse immunostained puncta within vestibular medial and inferior nuclei. Conclusion Glutamtatergic pathways participate in the processing of vestibular signals within VNC mainly through the re-uptake of glutamate into synaptic vesicles by VGluT1 and 2, whereas VGluT3 may play a similar role mainly in areas other than medial and inferior nuclei of VNC.
基金Supported by grant from Innovation Foundation of Nanjing Medical University(MC9901)
文摘Objective:To study the antitoxic role of vesicular monoamine transporter 2 (VMAT2) in transpgenic Chinese Hamster ovary(CHO) cell.Methods:With the technology of transgene from PC12 to CHO,MTT reduction assay was used to detect MPP^+ toxic effect on wild type CHO(wtCHO) and transgenic CHO.Meanwhile,the role of reserpine was also observed in MPP^+ toxic effects.Results:The sensitivity of transgenic CHO to MPP^+ was much less than that of wtCHO with 0.5 mmol/L MPP^+.Transgenic CHO had the same sensitivity as wtCHO if rotenone was given.WtCHO,by given reserpine alone,didn''''''''t change its sensitivity to MPP^+.Conclusions:VMAT2 has protective effect on transgenic CHO by transporting MPP^+ to vesicles.
文摘The processes of mitochondrial restitution are controlled by nuclear genes that encode proteins synthesized in ER and cytosol and delivered as organelle- and membrane-specific transport vesicles. The analysis of the transporters recovered from inner mitochondrial space (Mitosol) revealed that the ER-synthesized mitochondria-specific transport vesicles consist of two carriers, one remaining in outer mitochondrial membrane (OMM), and the other that transfers specific membrane segments to the inner mitochondrial membrane (IMM). The ER-assembled and IMM-committed membrane segments, while first integrated into OMM, undergo intra-mitochondrial lipid modification reflected in the synthesis of cardiolipin (CL) and inversion into Mitosol with load of IMM associated cytosolic proteins. Then, the CL-bedecked vesicles are released from OMM to Mitosol and upon contact with IMM fuse with the membrane, and the release of cytosolic cargo ensues. While ER-assembled mitochondria-specific transport vesicles fuse with OMM with the aid of the cytosolic, phosphatidylglycerol (PG)-specific phospholipase A2 (PLA2), the Mitosol-contained CL-specific PLA guides vesicles fusion with IMM. The described path of translocation of the membrane segments and the cytosol synthesized proteins into the designated mitochondrial compartments sustains growth and identity of OMM, IMM, maintains protein delivery for intra-mitochondrial lipid and protein modification in Mitosol, and ensures conformity of the cytosolic proteins cargo delivered to matrix.
基金Supported by FP7 IMI MIP-DILI:Mechanism-based integrated systems for the prediction of drug-induced liver injuryFP7 Eustroke,Health-F2-2008-202213:European Stroke Research Network+1 种基金TUDAS-1-2006-0029,OMFB-00505/2007:Development of HTS kit for analyzing transporter-drug interactions using cholesterol treated insect-cells expressing human MXR transporterGOP-1.1.1-11-2011-0017:Integrated preclinical tools for the determination and the enhancement of drug absorption
文摘The human body consists of several physiological barriers that express a number of membrane transporters. For an orally absorbed drug the intestinal, hepatic, renal and blood-brain barriers are of the greatest importance. The ATP-binding cassette(ABC) transporters that mediate cellular efflux and the solute carrier transporters that mostly mediate cellular uptake are the two superfamilies responsible for membrane transport of vast majority of drugs and drug metabolites. The total number of human transporters in the two superfamilies exceeds 400, and about 40-50 transporters have been characterized for drug transport. The latest Food and Drug Administration guidance focuses on P-glycoprotein, breast cancer resistance protein, organic anion transporting polypeptide 1B1(OATP1B1), OATP1B3, organic cation transporter 2(OCT2), and organic anion transporters 1(OAT1) and OAT3. The European Medicines Agency's shortlist additionally contains the bile salt export pump, OCT1, and the multidrug and toxin extrusion transporters, multidrug and toxin ex-trusion protein 1(MATE1) and MATE2/MATE2 K. A variety of transporter assays are available to test drugtransporter interactions, transporter-mediated drugdrug interactions, and transporter-mediated toxicity. The drug binding site of ABC transporters is accessible from the cytoplasm or the inner leaflet of the plasma membrane. Therefore, vesicular transport assays utilizing inside-out vesicles are commonly used assays, where the directionality of transport results in drugs being transported into the vesicle. Monolayer assays utilizing polarized cells expressing efflux transporters are the test systems suggested by regulatory agencies. However, in some monolayers, uptake transporters must be coexpressed with efflux transporters to assure detectable transport of low passive permeability drugs. For uptake transporters mediating cellular drug uptake, utilization of stable transfectants have been suggested. In vivo animal models complete the testing battery. Some issues, such as in vivo relevance, gender difference, age and ontogeny issues can only be addressed using in vivo models. Transporter specificity is provided by using knock-out or mutant models. Alternatively, chemical knock-outs can be employed. Compensatory changes are less likely when using chemical knockouts. On the other hand, specific inhibitors for some uptake transporters are not available, limiting the options to genetic knock-outs.
基金Supported by Grants from CONICET (PIP 6442)Agencia Nacional de Promoción Científica y Tecnológica (ANPCyT PICT 05-26115 and 05-26306),Argentina
文摘Vesicle-based traffi cking of hepatocellular transporters involves delivery of the newly-synthesized carriers from the rough endoplasmic reticulum to either the plasma membrane domain or to an endosomal,submembrane compartment,followed by exocytic targeting to the plasma membrane. Once delivered to the plasma membrane,the transporters usually undergo recycling between the plasma membrane and the endosomal compartment,which usually serves as a reservoir of pre-existing transporters available on demand. The balance between exocytic targeting and endocytic internalization from/to this recycling compartment is therefore a chief determinant of the overall capability of the liver epithelium to secrete bile and to detoxify endo and xenobiotics. Hence,it is a highly regulated process. Impaired regulation of this balance may lead to abnormal localization of these transporters,which results in bile secretory failure due to endocytic internalization of key transporters involved in bile formation. This occurs in several experimental models of hepatocellular cholestasis,and in most human cholestatic liver diseases. This review describes the molecular bases involved in the biology of the dynamic localization of hepatocellular transporters and its regulation,with a focus on the involvement of signaling pathways in this process. Their alterations in different experimental models of cholestasis and in human cholestatic liver disease are reviewed. In addition,the causes explaining the pathological condition (e.g. disorganization of actin or actin-transporter linkers) and the mediators involved (e.g. activation of cholestatic signaling transduction pathways) are also discussed. Finally,several experimental therapeutic approaches based upon the administration of compounds known to stimulate exocytic insertion of canalicular transporters (e.g. cAMP,tauroursodeoxycholate) are described.
文摘The synthesis of endoplasmic reticulum (ER)-derived transport vesicles is dictated by the contents and derivation of the cellular cytosol. The ER transport vesicles synthesized in the presence of gastric epithelial cells cytosol are destined for en bloc fusion with apical epithelial membrane, whereas those generated in hepa-tocytes-derived cytosol are destined for en bloc fusion with basolateral membrane. Moreover, during assembly of the dominant fraction of the apical or basolateral transport vesicles, a sub-stantial fraction of the vesicles is produced that fuses with endosomes, and the vesicles with still unknown destination that remain in cytosol. The process of ER vesicles synthesis is blocked by RNase treatment, whereas Golgi vesicles as-sembly is not affected. The experiments indicate that transport vesicles’ membrane composition and fidelity of its construction is defined in ER. The process involves synchronous membrane lipid synthesis, cotranslational intercalation of integral membrane proteins and containment of the vesicular cargo.
文摘Hrr25是酿酒酵母中Ⅰ型酪蛋白激酶家族成员,具有丝氨酸/苏氨酸蛋白激酶活性。其可以通过磷酸化多种蛋白质来发挥作用。Hrr25的底物蛋白质包括自噬相关蛋白、COPⅡ(coat protein complexes Ⅱ)囊泡衣被蛋白Sec24和Sec23、真核翻译起始因子6、γ-微管蛋白Tub4、延长器复合蛋白1等。另外Hrr25还可以与减数分裂重组蛋白Rec8、核孔蛋白Nup53、转录调节因子Crz1、转录激活因子Haa1等相互作用。Hrr25的多种相互作用蛋白质使其在自噬、囊泡运输、微管组装、减数分裂、有丝分裂、DNA修复、核糖体生物发生和弱有机酸胁迫途径等多种生物过程发挥作用。为了更好地了解Hrr25在各个生物过程中的作用机制以及各个生物过程之间的联系,本文总结了Hrr25的生物学功能及其作用机制,并概述其研究的潜在意义,为Hrr25的进一步研究提供理论依据。
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.31371436 and 8157051134 to Y.L.)by the laboratory start-up grant from Nanjing Medical University(to Y.L.).
文摘The endosomal trafficking of signaling membrane proteins, such as receptors, transporters and channels, is mediated by the retromer-mediated sorting machinery, composed of a cargo-selective vacuolar protein sorting trimer and a membrane-deforming subunit of sorting nexin proteins. Recent studies have shown that the isoforms, sorting nexin 5 (SNX5) and SNX6, have played distinctive regulatory roles in retrograde membrane trafficking. However, the molecular insight determined functional differences within the proteins remains unclear. We reported that SNX5 and SNX6 had distinct binding affinity to the cargo protein vesicular monoamine transporter 2 (VMAT2). SNX5, but not SNX6, specifically interacted with VMAT2 through the Phox domain, which contains an alpha-helix binding motif. Using chimeric mutagenesis, we identified that several key residues within this domain were unique in SNX5, but not SNX6, and played an auxiliary role in its binding to VMAT2. Importantly, we generated a set of mutant SNX6, in which the corresponding key residues were mutated to those in SNX5. In addition to the gain in binding affinity to VMAT2, their overexpression functionally rescued the altered retrograde trafficking of VMAT2 induced by siRNA-mediated depletion of SNX5. These data strongly suggest that SNX5 and SNX6 have different functions in retrograde membrane trafficking, which is determined by the different structural elements within the Phox domain of two proteins. Our work provides a new information on the role of SNX5 and SNX6 in the molecular regulation of retrograde membrane trafficking and vesicular membrane targeting in monoamine neurotransmission and neurological diseases.
