Hierarchy of protein assembly at the vertex ring domain for yeast vacuole docking and fusion

Vacuole tethering, docking, and fusion proteins assemble into a "vertex ring" around the apposed membranes of tethered vacuoles before catalyzing fusion. Inhibitors of the fusion reaction selectively interrupt protein assembly into the vertex ring, establishing a causal assembly hierarchy: (a) The Rab GTPase Ypt7p mediates vacuole tethering and forms the initial vertex ring, independent of t-SNAREs or actin; (b) F-actin disassembly and GTP-bound Ypt7p direct the localization of other fusion factors; (c) The t-SNAREs Vam3p and Vam7p regulate each other's vertex enrichment, but do not affect Ypt7p localization. The v-SNARE Vti1p is enriched at vertices by a distinct pathway that is independent of the t-SNAREs, whereas both t-SNAREs will localize to vertices when trans-pairing of SNAREs is blocked. Thus, trans-SNARE pairing is not required for SNARE vertex enrichment; and (d) The t-SNAREs regulate the vertex enrichment of both G-actin and the Ypt7p effector complex for homotypic fusion and vacuole protein sorting (HOPS). In accord with this hierarchy concept, the HOPS complex, at the end of the vertex assembly hierarchy, is most enriched at those vertices with abundant Ypt7p, which is at the start of the hierarchy. Our findings provide a unique view of the functional relationships between GTPases, SNAREs, and actin in membrane fusion.     

Differentiation-related changes in lipid classes with long-chain and very long-chain polyenoic fatty acids in rat spermatogenic cells

In rat seminiferous tubules (ST), cells that contain polar and neutral lipids with long-chain polyenoic fatty acids (PUFA) and sphingomyelins (SM) and ceramides (Cer) with very long chain (VLC) PUFA of the n-6 series coexist. In this study, pachytene spermatocytes and round spermatids were isolated to determine how these lipids change during spermatogenesis. As the amount per cell of PUFA-rich glycerophospholipids (GPL) decreased with cell size, the 22:5/20:4 ratio increased with cell differentiation. The elovl2 and elovl5 genes, required for 22:5 formation, were expressed (mRNA) in both cell types. Residual bodies- particles with compacted organelles and materials discarded from late spermatids-concentrated cholesterol, 22:5-rich triacylglycerols, and GPL, including plasmalogens and phosphatidylserine. Species of SM and Cer with nonhydroxylated (n-) VLCPUFA (28:4, 30:5, and 32:5) predominated in pachytene spermatocytes, whereas species with the corresponding 2-hydroxy (2-OH) VLCPUFA prevailed in round spermatids. Thus, a dramatic increase in the 2-OH/n-VLCPUFA ratio in SM and Cer was a hallmark of differentiation. A substantial decrease of 2-OH SM occurred between spermatids and mature spermatozoa and 2-OH SM species were collected in residual bodies “en route” to Sertoli cells. Notably, spermatids and spermatozoa gained a significant amount of ceramides devoid of n-VLCPUFA but having 2-OH VLCPUFA as their main fatty acids.     

Ceramides and sphingomyelins with high proportions of very long-chain polyunsaturated fatty acids in mammalian germ cells

Very long-chain polyunsaturated fatty acids (VLCPUFA) have previously been shown to be components of sphingomyelin (SM) of mammalian testis and spermatozoa. Here we examined the fatty acids of testicular ceramide (Cer) in comparison with those of SM in some mammals with a special focus on the rat testis. In bull, cat, dog, rabbit, mouse, and rat, VLCPUFA were found in both testicular lipids, Cer having a higher percentage of VLCPUFA than SM. Rat testis had the highest percentage of VLCPUFA in both lipids, the major ones being 28:4n-6 and 30:5n-6. VLCPUFA-containing SM and Cer occurred in cells located in the seminiferous tubules, where germ cells had a higher percentage of these species than Sertoli cells. Seminiferous tubule fractionation showed that SM and Cer of mitochondria and lysosomes had mostly saturates and negligible VLCPUFA, the latter being important in the SM and Cer of microsomes and other membrane fractions. VLCPUFA were absent from the SM and Cer of rat prepuberal testis, increased with the onset of spermatogenesis to account for nearly 15 and 40% of the total fatty acids of testicular SM and Cer, respectively, remained at those levels throughout the adult life of fertile rats and tended to decrease at advanced ages. Four conditions that lead to selective death of germ cells in vivo, namely experimental cryptorchidism, post-ischemic reperfusion, focalized x-ray irradiation and treatments with the antineoplasic drug doxorubicin, caused the VLCPUFA to disappear from the testicular SM and Cer of adult fertile rats, showing that these lipids are specific traits of spermatogenic cells.     

Effects of long-chain fatty acids on human urothelial cells in organ culture

It has been suggested that tumour-derived cells are differentially sensitive to the anti-proliferative and cytotoxic effects of long chain n-3 and n-6 polyunsaturated fatty acids (PuFAs). We have previously shown that PuFAs are also growth suppressive to highly proliferative normal human urinary bladder uro-epithelial (NHU) cells grown in monolayer culture. To determine if the effects on NHU cells are directly related to the proliferative index, we have studied the effects of long chain fatty acids in a bladder organ culture system, where proliferation and differentiation of the urothelium is under homeostatic control. A 50 microM concentration of fatty acids was chosen as this concentration of PuFA was profoundly growth inhibitory to NHU cells in monolayer culture. In organ culture, 50 microM PuFAs had no detectable effect on the proliferation or on the preservation of urothelial differentiated histioarchitecture, as assessed using a panel of phenotypic markers. These results suggest that the effects of PuFA may be modulated by the tissue microenvironment.     

Effects of arachidonic acid and the other long-chain fatty acids on the membrane currents in the squid giant axon

Summary The effects of arachidonic acid and some other long-chain fatty acids on the ionic currents of the voltage-clamped squid giant axon were investigated using intracellular application of the test substances. The effects of these acids, which are usually insoluble in solution, were examined by using -cyclodextrin as a solvent. -cyclodextrin itself had no effect on the excitable membrane. Arachidonic acid mainly suppresses the Na current but has little effect on the K current. These effects are completely reversed after washing with control solution. The concentration required to suppress the peak inward current by 50% (ED₅₀) was 0.18mm, which was 10 times larger than that of medium-chain fatty acids like 2-decenoic acid. The Hill number was 1.5 for arachidonic acid, which is almost the same value as for medium-chain fatty acids. This means that the mechanisms of the inhibition are similar in both long- and medium-chain fatty acids. When the long-chain fatty acids were compared, the efficacy of suppression of Na current was about the same value for arachidonic acid, docosatetraenoic acid and docosahexaenoic acid. The suppression effects of linoleic acid and linolenic acid on Na currents were one-third of that of arachidonic acid. Oleic acid had a small suppression effect and stearic acid had almost no effect on the Na current. The currents were fitted to equations similar to those proposed by Hodgkin and Huxley (Hodgkin, A.L., Huxley, A.F. (1952)J. Physiol (London) 117:500–544) and the change in the parameters of these equations in the presence of fatty acids were calculated. The curve of the steady-state activation parameter (m ) for the Na current against membrane potential and the time constant of activation ( _m ) were shifted 10 mV in a depolarizing direction by the application of fatty acids. The time constant for inactivation ( _h ) has almost unaffected by application of these fatty acids.     

Effects of monensin on vesicular transport pathways in the perfused rat liver

In the rat hepatocyte, the internalization and degradation of asialoglycoproteins and the secretion of plasma and biliary proteins require specific intracellular sorting of vesicles. To aid in the biochemical characterization of these different vesicular pathways, we examined the effects of the ionophore monensin on the uptake and degradation of 125I-asialoorosomucoid (ASOR) and on the secretion of plasma and biliary proteins by the in situ perfused rat liver. In control livers, 77% of injected 125I-ASOR was extracted on first pass; 93% of the extracted radioactivity was released back into the circulation (totally degraded and some intact ASOR was found); and approximately 2% was recovered in the bile, some of which was intact. Monensin treatment decreased first pass uptake of 125I-ASOR to 57% and abruptly blocked the release of radioactivity into the perfusate and the bile. When hepatic proteins were biosynthetically labeled with 3H-leucine, monensin treatment dramatically reduced and delayed the secretion of newly synthesized proteins into both the perfusate and the bile. In contrast with control livers, in which secretion of protein into the perfusate preceded secretion of protein into the bile, TCA-precipitable 3H-protein appeared in bile about 20 min before TCA-precipitable 3H-protein appeared in the perfusate in monensin-treated livers. Thus, monensin treatment in the perfused liver blocked the degradation of asialoglycoproteins and inhibited the secretion of plasma proteins but had less effect on biliary protein secretion. These data document physiologic effects of monensin in an intact organ and suggest that biochemical distinctions between different vesicular pathways exist in the rat hepatocyte.     

极长链脂肪酸的合成缺陷对酵母细胞膜的稳定性和多烯类药物敏感性的影响

【背景】脂肪酸延长酶家族参与脂肪酸代谢具有真核生物的高度保守性,且与膜脂的代谢密切相关。但细胞极长链脂肪酸(Very long-chain fatty acid,VLCFA)的合成缺陷对膜的稳定性及多烯类药物的敏感性影响并不完全明晰。【目的】探究细胞VLCFA延长酶ELO1、ELO2和ELO3的作用及功能。【方法】研究脂肪酸延长酶缺陷型elo1?、elo2?和elo3?对多烯类药物两性霉素B (Amphotericin B,AmB)、制霉菌素(Nystatin,Ny)及唑类硝酸益康唑(Econazolenitrate,Eco)的响应,检测不同酵母细胞的麦角固醇,检测其对Na+的响应及胞内钠钾离子水平。【结果】发现细胞VLCFA延长酶ELO2和ELO3缺陷后对AmB高度敏感;VLCFA延长酶缺陷突变株elo2?和elo3?对其它多烯类药物Ny及唑类药物Eco也十分敏感;细胞膜不饱和脂肪酸增加也会改变膜的稳定性,实验结果表明外源油酸(Oleic acid,OLA)增加了elo2?和elo3?突变体的AmB敏感性;相对野生型BY4741和elo1?,缺陷菌株elo2?和elo3?中麦角固醇的含量有显著下降;钠钾离子平衡是维护细胞正常生理的必要条件,也是检测细胞膜稳定性的重要参数,发现VLCFA的合成缺陷菌株对高浓度的NaCl比野生型菌株更敏感,使用ICP-AES检测不同浓度AmB胁迫下细胞内钠钾离子水平,也显示VLCFA延长酶缺陷菌株中,钠水平表现出上升趋势,并且细胞内钾含量明显降低。【结论】细胞VLCFA的合成缺陷会导致细胞膜更脆弱、稳定性下降,从而提高真菌对多烯类药物的敏感性,也表明脂肪酸延长酶是潜在的抗真菌治疗靶点。     

Binding of sulfosuccinimidyl fatty acids to adipocyte membrane proteins: Isolation and ammo-terminal sequence of an 88-kD protein implicated in transport of long-chain fatty acids

Summary We recently reported (Harmon et al., J. Membrane Biol. 124:261–268, 1991) that sulfo-N-succinimidyl derivatives of long-chain fatty acids (SS-FA) specifically inhibited transport of oleate by rat adipocytes. These compounds bound to an 85–90 kD membrane protein which was also labeled by another inhibitor of FA transport [³H]DIDS (4,4-diisothiocyanostilbene-2-2-sulfonate). These results indicated that the protein was a strong candidate as the transporter for long-chain fatty acids. In this report we determined that the apparent size of the protein is 88 kD and its isoelectric point is 6.9. We used [³H]SS-oleate (SSO), which specifically labels the 88-kD protein, to isolate it from rat adipocyte plasma membranes. Identification of 15 amino acids at the N-terminus region revealed strong sequence homology with two previously described membrane glycoproteins: CD36, a ubiquitous protein originally identified in platelets and PAS IV, a protein that is enriched in the apical membranes of lipidsecreting mammary cells during lactation. Antibody against PAS IV cross-reacted with the adipocyte protein. This, together with the N-terminal sequence homology, suggested that the adipocyte protein belongs to a family of related intrinsic membrane proteins which include CD36 and PAS IV.     

Membrane tethering and fusion in the secretory and endocytic pathways

Studies of intracellular trafficking over the past decade or so have led to striking advances in our understanding of the molecular processes by which transport intermediates dock and fuse. SNARE proteins play a central role, assembling into complexes that bridge membranes and may catalyze membrane fusion directly. In general, different SNARE proteins operate in different intracellular trafficking pathways, so recent reports that SNARE assembly in vitro is promiscuous have come as something of a surprise. We propose a model in which proper SNARE assembly is under kinetic control, orchestrated by members of the Sec1 protein family, small GTP-binding Rab proteins, and a diverse assortment of tethering proteins.     

Ceramides with 2-hydroxylated,very long-chain polyenoic fatty acids in rodents: From testis to fertilization-competent spermatozoa

Sphingolipids from rodent testis and spermatozoa are known to contain non-hydroxylated (N-) and 2-hydroxylated (2-OH) very-long-chain polyunsaturated fatty acids (VLCPUFA). In this study, the contribution of species with each type of fatty acids to the total ceramides (Cer) and sphingomyelins (SM) was investigated in rat and mouse testis and in rat spermatozoa. The major VLCPUFA in both lipids of testis were N- and 2-OH versions of 28:4n−6, 30:5n−6 and 32:5n−6 in the rat, and predominantly of 30:5n−6 in the mouse. Absent altogether from rat pre-puberal testes, SM and Cer with N-VLCPUFA appeared 10 days earlier than those with 2-OH VLCPUFA in postnatal development, in association with germ cell differentiation. Conversely, in adult fertile rats that were gradually deprived of germ cells in vivo after treatment with doxorubicin, SM and Cer with N-VLCPUFA decreased earlier than their 2-OH counterparts, and neither was present in aspermatogenic testes. In rat epididymal spermatozoa, the content of Cer prevailed over that of SM and 2-OH VLCPUFA prevailed over N-VLCPUFA in both lipids. In mature gametes, the acrosomal reaction resulted in an almost complete hydrolysis of the species of SM that contain both types of VLCPUFA to produce the corresponding Cer. Ceramides are biosynthetic precursors of SM in the testis, but themselves final products in spermatozoa. VLCPUFA-rich SM and Cer are thus produced in germ cells with the teleological objective of fulfilling their ultimate physiological role in spermatozoa that are apt and ready to fertilize an oocyte.     

A role for the Rab6B Bicaudal-D1 interaction in retrograde transport in neuronal cells

The Rab6 subfamily of small GTPases consists of three different isoforms: Rab6A, Rab6A' and Rab6B. Both Rab6A and Rab6A' are ubiquitously expressed whereas Rab6B is predominantly expressed in brain. Recent studies have shown that Rab6A' is the isoform regulating the retrograde transport from late endosomes via the Golgi to the ER and in the transition from anaphase to metaphase during mitosis. Since the role of Rab6B is still ill defined, we set out to characterize its intracellular environment and dynamic behavior. In a Y-2H search for novel Rab6 interacting proteins, we identified Bicaudal-D1, a large coiled-coil protein known to bind to the dynein/dynactin complex and previously shown to be a binding partner for Rab6A/Rab6A'. Co-immunoprecipitation studies and pull down assays confirmed that Bicaudal-D1 also interacts with Rab6B in its active form. Using confocal laser scanning microscopy it was established that Rab6B and Bicaudal-D1 co-localize at the Golgi and vesicles that align along microtubules. Furthermore, both proteins co-localized with dynein in neurites of SK-N-SH cells. Live cell imaging revealed bi-directional movement of EGFP-Rab6B structures in SK-N-SH neurites. We conclude from our data that the brain-specific Rab6B via Bicaudal-D1 is linked to the dynein/dynactin complex, suggesting a regulatory role for Rab6B in the retrograde transport of cargo in neuronal cells.     

Effects of fatty acids on membrane currents in the squid giant axon

Summary The effects of fatty acids on the ionic currents of the voltage-clamped squid giant axon were investigated using intracellular and extracellular application of the test substances. Fatty acids mainly suppress the Na current but have little effect on the K current. These effects are completely reversed after washing with control solution. The concentrations required to suppress the peak inward current by 50% and Hill number were determined for each fatty acid. ED₅₀ decreased about 1/3 for each increase of one carbon atom. The standard free energy was –3.05 kJ mole^–1 for CH₂. The Hill number was 1.58 for 2-decenoic acid. The suppression effect of the fatty acids depends on the number of carbon atoms in the compounds and their chemical structure. Suppression of the Na current was clearly observed when the number of carbon atoms exceeded eight. When fatty acids of the same chain length were compared, 2-decenoic acid had strong inhibitory activity, but sebacic acid had no effect at all on the Na channel. The currents were fitted to equations similar to those proposed by Hodgkin and Huxley (J. Physiol. (London) 117:500–544, 1952) and the changes in the parameters of these equations in the presence of fatty acids were calculated. The curve of the steady-state activation parameter (m ) for the Na current against membrane potential and the time constant of activation ({ie113-1}) were shifted 20 mV in a depolarizing direction by the application of fatty acids. The time constant for inactivation ({ie113-2}) was almost no change by application of the fatty acids. The time constant for activation ({ie113-3}) of K current was shifted 20 mV in a depolarizing direction by the application of the fatty acids.     

Multiple Roles of VARP in Endosomal Trafficking: Rabs,Retromer Components and R‐SNARE VAMP7 Meet on VARP

VARP (VPS9‐ankyrin‐repeat protein, also known as ANKRD27) was originally identified as an N‐terminal VPS9 (vacuolar protein sorting 9)‐domain‐containing protein that possesses guanine nucleotide exchange factor (GEF) activity toward small GTPase Rab21 and contains two ankyrin repeat (ANKR) domains in its central region. A number of VARP‐interacting molecules have been identified during the past five years, and considerable attention is now being directed to the multiple roles of VARP in endosomal trafficking. More specifically, VARP is now known to interact with three different types of key membrane trafficking regulators, i.e. small GTPase Rabs (Rab32, Rab38 and Rab40C), the retromer complex (a sorting nexin dimer, VPS26, VPS29 and VPS35) and R‐SNARE VAMP7. By binding to several of these molecules, VARP regulates endosomal trafficking, which underlies a variety of cellular events, including melanogenic enzyme trafficking to melanosomes, dendrite outgrowth of melanocytes, neurite outgrowth and retromer‐mediated endosome‐to‐plasma membrane sorting of transmembrane proteins.      

Cargo selection in vesicular transport: the making and breaking of a coat

Intracellular traffic is mediated by vesicular/tubular carriers. The carriers are formed by the activity of cytosolic coat proteins that are recruited to their target membranes and deform these membranes into buds and vesicles. Specific interactions between recruited coat subunits and short peptide sequences (transport motifs) on cargo proteins direct the incorporation of cargo into budded vesicles. Here, we focus on cargo selection reactions mediated by COPII and AP-2/clathrin vesicle coat complexes to explore common mechanisms by which coat assembly support localized and selective cargo sorting. Recent findings suggest that multiple, low-affinity interactions are employed in a cooperative manner to support coat assembly and enable cargo recognition. Thus low-binding affinities between coat subunits and transport motifs are transiently transformed into high-avidity, multivalent and selective interactions at vesicle bud sites. The temporal and regulated nature of the interactions provide the key to cargo selection.     

A deubiquitinating enzyme UBPY regulates the level of protein ubiquitination on endosomes

Monoubiquitination of endocytosed cell surface receptors serves as a sorting signal for their trafficking from endosomes to lysosomes. The sorting of ubiquitinated proteins is executed by concerted actions of class E vacuolar protein sorting (Vps) proteins. Some proteins in the sorting machinery undergo monoubiquitination, suggesting that their functions are also regulated by ubiquitination. The Hrs-STAM complex, a class E Vps protein complex essential for the initial step of the sorting pathway, binds two deubiquitinating enzymes, UBPY and AMSH. Here we examined the effects of inactivating UBPY on protein ubiquitination at endosomes. Overexpression of a catalytically inactive UBPY mutant or depletion of UBPY by RNA interference resulted in the accumulation of ubiquitinated proteins on morphologically aberrant endosomes. Electron microscopy showed that they are aggregates of multivesicular endosomes. Among the sorting machinery proteins that undergo ubiquitination, Eps15 was monoubiquitinated at an elevated level in UBPY-inactivated cells. UBPY also deubiquitinated Eps15 in vitro, suggesting that Eps15 is a cellular substrate for UBPY. Furthermore, inactivation of UBPY caused the accumulation of Eps15 on the endosomal aggregates. These results suggest that UBPY regulates the level of protein ubiquitination on endosomes, which is required for maintaining the morphology of the organelle.     

Effects of non-esterified fatty acids on bovine granulosa cells and developmental potential of oocytes in vitro

Cryopreservation of bull semen is sub-optimal, causing cell death of a majority of spermatozoa. Even the surviving cells are affected post-thaw, either structurally or functionally. The aim of this study was to investigate the sequence of events that take place when sperm plasma membrane and acrosome deteriorate during a 4 h incubation period post-thaw, with special attention paid to the acrosome status of dying cells. Frozen-thawed semen of six AI dairy bulls was used. Three straws per batch were pooled and incubated at 37 °C. Sub-samples were taken at 30 min intervals and stained with SYBR 14, propidium iodide (PI) and phycoerythrin-conjugated peanut agglutinin (PE-PNA). Plasma membrane and acrosome integrity were measured by flow cytometry. The experiment was repeated three times. Immediately after thawing, only 3.45% of the dying cells showed acrosomal exocytosis. This number increased dramatically during incubation, reaching 67% after 4 h. Within the intact cell population, the overall decrease in viability and acrosome integrity was kept at five percentage points. Flow cytometry and the triple fluorochrome combination presented a detailed picture of the time course in plasma membrane and acrosome deterioration of frozen-thawed bull semen. The results are expected to be useful for monitoring new cryopreservation protocols.     

Rab GTPases regulating receptor trafficking at the late endosome–lysosome membranes

Lysosomes serve key degradative functions for the turnover of membrane lipids and protein components. Its biogenesis is principally dependent on exocytic traffic from the late endosome via the trans‐Golgi network, and it also receives cargo to be degraded from the endocytic pathway. Membrane trafficking to the late endosome–lysosome is tightly regulated to maintain the amplitude of signalling events and cellular homeostasis. Key coordinators of lysosomal traffic include members of the Rab small GTPase family. Amongst these, Rab7, Rab9 and the more recently studied Rab22B/31 have all been reported to regulate membrane trafficking processed at the late endosome–lysosome system. We discuss what is known about the roles of these Rab proteins and their interacting partners on the regulation of traffic of important receptor proteins such as the epidermal growth factor receptor (EGFR) and the mannose 6‐phosphate receptor (M6PR), in association with the late endosome–lysosome system. Better knowledge of EGFR and M6PR traffic in this regard may aid in understanding the pathological processes, such as oncogenic transformations associated with these receptors. Copyright © 2012 John Wiley & Sons, Ltd.     

四个脂肪酸合成酶基因在哺乳动物细胞中的超表达提高长链多不饱和脂肪酸生物合成效率

DHA(22:6n-3)、EPA(20:5n-3)和ARA(20:4n-6)三种长链多不饱和脂肪酸在生物体内活性最强,它们在促进大脑发育和功能维持以及在预防和治疗心血管疾病、炎症、癌症等多种疾病方面有着重要作用。然而,尽管哺乳动物体内有完整的长链多不饱和脂肪酸合成酶系,但哺乳动物合成这些长链多不饱和脂肪酸的效率很低而主要依赖于食物获取。本研究应用转基因方法,将哺乳动物来源的Δ6和Δ5脂肪酸去饱和酶以及Δ6和Δ5脂肪酸延长酶这4种酶的编码基因构建成为一个多基因表达载体,然后转染哺乳动物细胞HEK293T,实现了4个目的基因的超表达,再通过气质联用(GC-MS)分析证实了DHA、EPA和ARA等长链多不饱和脂肪酸的合成效率及水平显著增加,DHA的水平更是提高了2.5倍。由此可见,哺乳动物具有某种抑制长链多不饱和脂肪酸高水平合成的机制,但通过Δ6和Δ5脂肪酸去饱和酶以及Δ6和Δ5脂肪酸延长酶的超表达,能够打破哺乳动物这种抑制机制,从而显著提高DHA、EPA、ARA等的合成水平。同时,本研究的思路也为在转基因动物中生产长链多不饱和脂肪酸提供了重要的启示。     

多不饱和脂肪酸对微生物低温适应性的影响

地球生物圈75%以上的环境温度常年低于5℃,在这种低温环境中栖息着多种适应低温的微生物。在长期进化过程中低温微生物从细胞到分子水平形成一套独特的低温环境适应机制,而通过增加细胞膜膜脂中多不饱和脂肪酸含量来维持低温条件下最佳的细胞膜流动性是其中的一种。从多不饱和脂肪酸对微生物低温生长、细胞膜流动性细胞膜蛋白的组成和表达水平的影响来探讨多不饱和脂肪酸与微生物低温适应性的关系,总结多不饱和脂肪酸低温合成调节机制的研究进展,为相关的基础和应用开发研究提供参考。