Golgi matrix is composed ofUnit membraneIt is composed of flat capsules stacked together.The flat sac is round, with enlarged edges and perforation.All Golgi apparatus in a cell are collectively called Golgi apparatus.[1]
A Golgi apparatus usually has 5 – 8 sacs with liquid insideInclusion。[1]
Golgi apparatus (Golgi complex) is also called Golgi complex and Golgi organ.By lightfacial maskIt consists of sacculesVesicle(vacuoles) and vesicles.yesEukaryotic cellinEndometrial systemOne of the components of.
Golgi apparatus (Golgi bodies) is composed of many flatVesicleComposed mainly of secretionOrganelle。Also called Golgi apparatus or Golgi complex;In higher educationplant cellMiddle scaleDispersed golgi。
In the more than 100 years of Golgi's history since its discovery, more than half of the time was spent debating the shape of Golgi's body and even whether it really existed.
cytologyMany people believe that Golgi apparatus is an artificial illusion caused by fixation and dyeing.
Golgi is composed of several flatVesicleStacked together to form highly polarOrganelles.[3]
Often distributed inEndoplasmic reticulumAndcell membraneIt is arched or hemispherical, and the convex side facing the endoplasmic reticulum is called forming face or cis face.The concave side facesplasma membraneIt is called mature face or trans face.[3]
There are some big or small ones on the front and backTransport vesicleIn polar cells, Golgi bodies are often distributed in large numbers at the secretory endcytoplasmMedium.Because it looks very similarSmooth endoplasmic reticulumTherefore, some scientists believe that it evolved from the smooth endoplasmic reticulum.[3]
Cellular structure
The diameter of the flat capsule is 1μm. It is composed of a single layer of membrane with a thickness of 6-7nm, and a cavity is formed in the middle. The periphery is mostly bubble shaped, with 4-8 flat cysts togetheralgaeUp to ten or twenty, which constitute the main body of Golgi body, are called Golgi stacks.
Golgi membraneIt contains about 60% protein and 40%lipidIt has some protein components common to Endoplasmic Reticulum.Membranous lipidThe content of phosphatidylcholine in is between Endoplasmic Reticulum and plasma membrane, and neutral lipids mainly includecholesterol，Cholesterol esterandtriglyceride。
Golgi apparatus consists of two typesmembrane structureNamely, the flat membrane capsule is composed of vesicles of different sizes.Its surface looks very similarSmooth endoplasmic reticulum。The flattened capsule is the most characteristic structural component of Golgi apparatus.
In generalplant cellIn the middle, 3~7 flat membranous sacs overlap and are slightly arched.Arcuate vesicularConvex surfaceIt is called formative surface or immature surface;Concave surface is called secretory surface, or mature surface.SmallvacuoleScattered around the flat membrane capsule, mostly concentrated near the formation surface.
It is generally believed that small vacuoles are formed by budding endoplasmic reticulum near Golgi apparatus, which plays a role in transporting substances from endoplasmic reticulum to Golgi apparatus.Rough endoplasmic reticulumIntracavityprotein, germinatingVesicleIt is transported to Golgi body and processed gradually from formation surface to mature surface.The larger vacuoles are formed by the local expansion of the end of the flat membrane capsule or the secretory surface and then disconnection.Because the vacuole contains the secretion of the flat membrane sac, it is also calledSecretory vesicle。The secretory vesicles gradually move towardscell surface, and the cytoplasm of cellsMembrane fusion, and then burst,InclusionThen discharge.The number and development of Golgi apparatus in different cells depend not only on the type and differentiation of cells, but also on the physiological state of cells.
major function
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The main functions of Golgi apparatus will beEndoplasmic reticulumThe proteins synthesized on the cell surface are processed, sorted, and transported, and then sent to specific parts of the cell or secreted out of the cell.
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Golgi base is completeCell secretionThe place where materials (such as protein) are finally processed and packaged.[3]
The vesicles sent from the endoplasmic reticulum fuse with the Golgi body membrane, and send the contents into GolgiCoelomWhere the newly synthesized proteinPeptide chainContinue with finishing and packaging.[3]
Golgi apparatus also synthesizes some extracellularPolysaccharideAnd materials for modifying cell membranes.[3]
Protein glycosylation
N – The synthesis of linked sugar chains starts from the endoplasmic reticulum and is completed in the Golgi apparatus.stayEndoplasmic reticulumFormedglycoproteinHave similarsugar chainAfter entering Golgi apparatus from Cis surface, a series of orderly processing and modification took place in the transport process between membrane capsules. Most of the original sugar chainmannoseIt is excised, but different types of sugar molecules are added by various glycosyltransferases in turn to form oligosaccharide chains with different structures.Glycoproteinspace structureDetermines which glycosyltransferase it can combine with to produce specificGlycosylationmodification.
Many glycoproteins have both N-linked and O-linked sugar chains.O – ConnectedGlycosylChemization is only carried out in Golgi apparatus, and usually a sugar unit connected is N-acetylGalactose, the connecting parts are SerThrAnd Hyp'sOHGroup, and then successively transfer the sugar group to it to form an oligosaccharide chain. The sugar donor is alsonucleosideSugar, such as UDP – galactose.Glycosylation results in different proteins being labeled differently, changing theconformationAnd increase protein stability.
It is responsible for processing, classifying and transporting the proteins synthesized by cellsSynthetic protein→ enter ER cavity → form vesicles by budding → enter CGN → enterculture medium(medium) Gdgi processing → forming vesicles in TGN → vesicles fusing with plasma membrane and discharging.
According to the observation of early light microscope, it has been proposed that Golgi apparatus is related to the secretory activity of cells.
With the development of modern scienceCytochemistryandAutoradiographyThis view is further confirmed and developed.The role of Golgi apparatus in the secretion activity is mainly to process (such as concentration or segregation), store and transport the protein substances transported from rough endoplasmic reticulum, and finally form secretion vesicles.When the formed secretory vesicle is disconnected from the Golgi vesicle, the secretory vesicle membrane contains GolgiCapsuleThe enzymes contained can also play a role in promoting the concentration and maturation of secretory particles, and finally expel them out of the cell.Most typical, such as pancreasExocrine cellThe zymogen particles formed in.
Autoradiography technology proves that Golgi apparatus itself can synthesize certain substances, such asPolysaccharides。It can also synthesize protein with sugar or fatglycoproteinandLipoproteinForm of.In some cells (e.gHepatocyte）Golgi apparatus is also related to the synthesis and secretion of lipoproteins.
Conduct membrane conversion
The membrane of Golgi apparatus is inEndoplasmic reticulumandplasma membraneTherefore, Golgi apparatus performs the function of membrane transformation. After the new membrane synthesized on the endoplasmic reticulum is transferred to Golgi apparatus, it is modified and processed to form a fusion with the transport vesicular plasma membrane, so that the newly formed membrane can be integrated onto the plasma membrane.
Hydrolyze protein
If proteinN-endorC-endCut off and become active substance（insulinC terminal) or hydrolyze the precursor containing multiple identical amino sequences into an active polypeptide, such asneuropeptide。
Participate in the formation of lysosomes
It is generally believed thatPrimary lysosomeThe formation process of Golgi vesicles is similar to that of secretory granules, and also originates from Golgi vesicles.primarylysosomeIt is essentially identical with secretory granules (mainly some zymogen granules), because lysosomes contain a variety of enzymes (mainly varioushydrolase）Protein, like zymogen particles, also participates inDecomposition metaboliteRole of.The difference is that the zymogen particles are discharged from the outside of the cell to play a role, while the enzymes in the lysosome mainly play a role in the cell.
Participate in the formation of plant cell wall
Golgi apparatus
Filaments in higher plant cellsAnaphase, formingcell wallThe number of Golgi apparatus increased.In plant cells, Golgi apparatus synthesizes and secretes a variety of polysaccharides, which contain at least 12 kinds ofmonosaccharide。Most polysaccharides are branched and have manyCovalentDecoration, far more thanAnimal cellThe complexity of.It is estimated that it is typical of plant cellsPrimary wallThe process involves hundreds of enzymes.
Most enzymes exist in the endoplasmic reticulum and Golgi apparatus, except for a few enzymes that covalently bind to the cell wall.One exception is that the cellulose of most plant cells is from the outside of the cell membranesynthetaseSynthetic.
In plant cell division, Golgi apparatus is related to the formation of cell wall.In high school textbooks, it is believed that Golgi apparatus can synthesize cellulose, but in fact, cellulose in most plant cells is synthesized by cellulose synthase outside the cell membrane.It is clear that Golgi bodies can be synthesizedpectinAnd non cellulose polysaccharides.
Other functions
Golgi has other functions.As in someprotozoanGolgi apparatus is related to regulating the liquid balance of cells.
After receiving the newly synthesized substances from the endoplasmic reticulum and classifying them, most of them are transferred into the Golgi intermediate membrane capsule, and a small part of the proteins andlipidThen return to the endoplasmic reticulum (resident on the endoplasmic reticulum).Others, such as protein O – connection,Transmembrane proteinAcylation of, CoronaVirusesThe assembly of is also here.
Ph was lower than other parts.The function is protein classification, packaging and output, and "late" protein modification.And ensure that protein and lipidOne-way transshipment。
Involvement of inflammatory reaction
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Golgi reverse membrane capsulenetwork structure（TGN）Recently, it was found that it can participate in inflammatory bodies (also known as“Inflammatory corpuscle”Here, the receptor protein of inflammasome is NLRP3), which responds to external signals and then assembles the signal axis.[1]
Inflammatory body is a protein complex, mainly including receptor protein, adaptor protein ASC and downstreamCystatincaspase–1。The types and functions of inflammatory bodies are complex, so I will not repeat them here.For NLRP3 receptor protein, its structural composition is as follows:[1]
The downstream connector protein ASC has the following structure:
After the receptor protein is activated, it can pass through its own PYDDomainAndAdaptor proteinPYD domain of to activateASCThen the latter activates downstream caspase-1 through its own CARD domain, prompting it to self cut into two parts, further cutting and promoting cellsInterleukinEtccell factorThe maturity of.
In PYD and NACHTDomainThere are highly conservativepositive electricityRegion, which contains only 4 amino acids KKKKPhantomAll known NLRP3 gene proteins contain at least three positive chargesamino acid。When receiving inflammatory bodyAgonistTGN is found to disintegrate into vesicular structures (dTGN)negative electricityphospholipidPtdIns4P can communicate with NLRP3positive chargeAnd promote the latter to form polymer, thereby activating NLRP3.
To some extent, this mechanismbreakThe impression of TGN as a fixed component of Golgi apparatus was created, and Golgi apparatus as ainflammatory reaction Signal axis "messenger"New identity。[1]
Action process
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In cellsproteinSynthesis of fromnucleusInGenomic DNATranscriptional synthesisMessenger RNA（mRNA）At first, mRNA passed through the nucleus to the outsideEndoplasmic reticulum(ER), and the protein will be transferred from the endoplasmic reticulumVesicleThe destination is the logistics center Golgi, just like the goods produced in the factory are transported to the logistics center and then distributed to users.
In fact, the destination of the protein has been marked on the protein transported to Golgi apparatus, just like the consignee address will be pasted when the goods enter the logistics center.At this time, Golgi apparatus will read the "receiving address" of the protein. If there is a "secretion" signal on the protein, Golgi apparatus will know that the protein needs to be secreted out of the cell, so it will form aSecretory proteinTo the small extracellular vesicles, the proteins that need to be secreted outside the cells are wrapped inside and finally secreted outside the cells.If there isSignal representationThe protein should be left in the endoplasmic reticulum, and Golgi apparatus will form another small vesicle to send the protein back to ER.Golgi then sends the protein to the "consignee" by reading the information on the protein.
Golgi Logistics Center not only has these functions, but also processes the transported goods - protein. This process is toOligosaccharide Connect to the protein. This process is calledGlycosylationThis glycosylation is the guarantee that the protein can finally perform various functions.
pathological changes
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1. Golgi hypertrophy.Golgi hypertrophy occurs when cell secretions and enzymes are produced vigorously.macrophageWhen the phagocytosis activity is strong, manyPhagosome, Golgi complex increases and many Golgi are broken from itVesicle。
2. Golgi atrophy.Golgi apparatus became smaller and partially disappeared when various cells were atrophied.
3. Golgi damage.Most of them showed the expansion of flat bursa and the disintegration of flat bursa, bullae and vesicles.
