lysosomes and peroxisomes.pdf
TRANSCRIPT
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Lysosomes and Peroxisomes
M.Nagalingam
PhD Scholar (P-1737)
IVRI, Izatnagar
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Introduction
Lysosomes (Gr., lyso=digestive + soma=body)
Lysosomes are dynamic organelles that receive and degrade
macromolecules from the secretory, endocytic, autophagic and
phagocytic membrane-trafficking pathways.
The lysosomal lumen is maintained at an acidic pH (around 5) by
an ATP-driven proton pump in the membrane.
C. de Duve and his coworkers (1963, 1964, 1974) worked in
Belgium and their approach was biochemical one.
Alex Novikoffand his research group (1962, 1964) worked in
United States and their approach was morphological and
cytochemical
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The lysosomes occur in most animal (except mature
erythrocytes) cells
The lysosomes are round vacuolar structures which remain
filled with dense material and are bounded by single unit
membrane.
Their shape and density vary greatly.
Lysosomes are 0.2 to 0.5m in size. Since, size and shape of
lysosomes vary from cell to cell and time to time (i.e.they arepolymorphic), their identification becomes difficult.
Lysosomes
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Classes of proteins :
Soluble lysosomal hydrolases(also referred to as acidhydrolases) 50 known lysosomal hydrolases
Integral lysosomal membrane proteins (LMPs)
~25 LMPslysosomeassociated membrane protein 1 (LAMP1)
LAMP2,
lysosome integral membrane protein 2 (LIMP2; also
known as SCARB2)tetraspanin CD63
Adaptor proteins AP1, AP3
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Trans Golgi Network
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Targeting of lysosomal proteins by phosphorylation of
mannose residues
Phosphate groups to the 6 position of mannose residues
N-acetylglucosamine phosphates to lysosomal proteins from UDP-N-
acetylglucosamine
Recognition by signal patches
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Endocytosis and lysosome formation
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Possible interaction between endocytosis and biogenesis
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Early endosomes
early endosomal antigen 1 (EEA1) and Rab5 are widely
used as markers
Late endosomes vs lysosomes
lack of M6P receptors in lysosomes
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Clathrins
Recycling of M6PRs by endosometoTGN carriers will not require clathrin ,
but requires the retromer subunit sorting nexin 1 (SNX1) and/or SNX2
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Mannose 6 phosphate independent pathway
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Two major degradation routes:
The lysosomal network and
the ubiquitin-proteasome system .
Proteases
Cathepsin family of proteases
serine (A and G),
Cysteine (B, C, F, H, K, L, O, S, V, W, and X), and aspartic
cathepsins (Dand E).
pH:Vacuolar H+-ATPase, a transmembrane multimeric protein
complex
Degradative function
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Lysosomes in phagocytosis and autophagy
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Autophagy in mammalian cells
Chaperone-mediated autophagy,
Microautophagy,
Macroautophagy
mammalian target of rapamycin (mTOR)
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Lysosomal exocytosis
Lysosomal exocytosis plays a major role in important processes
such as immune responses, bone resorption, cell signaling, andplasma membrane repair
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Evasion of lysosome fusion by microbes
Preventi ng lysosome fusi on -Escherichia coli K1
Delayin g phagolysosome biogenesis-Salmonella
enterica and Mycobacterium tuberculosis
Escaping the phagosome-Listeria, Shigella andRickettsia
Legionella pneumophila, Coxiellabrunetti and Brucella
abortus, can reside in an autophagosomal compartment
where they multiply
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Lysosomal storage disorders
Over50 human lysosomal storage conditions have been recognized, and
although individually rare, their combined prevalence is1in 8000 births
Most of these disorders are autosomal recessively inherited such as Niemann-
Pick disease, type C, however a few are X-linked recessively inherited, such as
Fabry disease and Hunter syndrome (MPS II).
Lysosomal storage disorders frequently involve the central nervous system
L l di d
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Tay-Sachs disease was the first lysosomal storagedisorder (LSD) described, in 1881
Gaucher disease was the second, in 1882
The first link between an enzyme deficiency and aLSD (-glucosidase and Pompe disease) waspublished in 1963 by Hers
The successful treatment of a LSD, Gaucherdisease with -glucosidase, became available in theearly 1990s
Pompe became the first disease formallyrecognized as a lysosomal storage disorder.
Ernest GAUCHER(1854-1919)
Lysosomal storage disorders
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Biochemical and Cellular basis of LSDs
Futerman AH & van Meer G (2004) 5:554-565
1 catalytic activity
2 activator
3 misfolding
4 multienzyme complex
5 glycosylation
6 M-6-P targetting
7 other transport steps
8 membrane transporters
9 membrane regulators
L l di d
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Type of defect protein Disease examples Deficient protein
Lysosomal enzymes primarily
Tay-Sachs disease, I-cell
disease,Sphingolipidoses
(e.g., gangliosidosis, Gaucherand Niemann-Pick disease)
Various
Posttranslational modification of
enzymesMultiple sulfatase deficiency Multiple sulfatases
Membrane transport proteins Mucolipidosis type II and IIIAN-acetylglucosamine-1-phosphate
transferase
Enzyme protecting proteins Galactosialidosis Cathepsin A
Soluble nonenzymatic proteinsGM2-AP deficiency, variant
AB, Niemann-Pick disease, type C2GM2-AP, NPC2
Transmembrane proteins
SAP deficiency Sphingolipid activator proteins
Niemann-Pick disease, type C1 NPC1
Salla disease Sialin
Lysosomal storage disorders
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MPS I (Hurler, Hurler-Scheie, Scheie)
MPS II (Hunter)
MPS III (San filipo Types A,B,C and D)MPS IV (Morquio type A and B)
MPS VI (Maroteaux-Lamy)
MPS VII (Sly)MPS IX (Hyaluronidase deficiency)
Multiple Sulfatase deficiency
I - Defective metabolism of glycosaminoglycans
" the mucopolysaccharidoses"
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Aspartylglucosaminuria
Fucosidosis, type I and II
Mannosidosis
Sialidosis, type I and II
II - Defective degradation of glycan
portion of glycoproteins
III - Defective degradation of glycogen
Pompe disease
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Acid sphingomyelinase deficiency (Niemann-Pick A & B)
Fabry disease
Farber disease
Gaucher disease, type I, II and III
GM1 gangliosidosis, type I, II and III
GM2 gangliosidosis (Tay-Sachs type I, II, III and Sandhoff
Krabbe disease
Metachromatic leukodystrophy, type I, II and III
IV - Defective degradation of sphingolipid
components
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V - Defective degradation of polypeptides
Pycnodysostosis
VI - Defective degradation or transport of
cholesterol, cholesterol esters, or other
complex lipids
Neuronal ceroid lipofuscinosis, type I, II, III and IV
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I-cell disease Caused by the deficiency of an enzyme(N-acetyglucosamine
phosphotransferase) Because of the absence of this enzyme,thesecreted enzymes lack the mannose phosphate residues whichis a signal for targeting lysosomal enzymes to lysosomes.
Symptoms:a rare inherited metabolic disorder characterized bycoarse facial features,skeletal abnormalities and mentalretardation .Many cells from these patients contain lysosomesthat are bloated with undegraded materials. back
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Peroxisomes
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C.de Duve and P. Baudhuin (1966) coined the term peroxisome for the
micro-bodies of mammalian systems and studied their structure and
function.
Called them peroxisomes because they generate and destroy H2O2
All animal cells (except erythrocytes) contain peroxisomes.
Peroxisomes are related to specialized peroxisomes called glycosomes in
parasites such as Trypanosomes, and to plant glyoxysomes
Peroxisomes
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~60 known enzymes in the matrix and ~45 documented
integral or peripheral membrane proteins
Peroxisomes are surrounded by a single membrane and they
range in diameter from 0.1 to 1m
They have crystalline and non-crystalline inclusions.
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Assembly of peroxisomes
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Pex3 is an integral
transmembrane
protein
Pexl9 is a
farnesylated protein
found largely in the
cytosol.
Assembly of peroxisomes
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Protein Import C-terminal signal
sequence: SKL(PTS1)
N-terminal signalsequence: RLX5HL
(PTS2)
Proteins involved inimport: peroxins
Import driven byATP hydrolysis
Dont have to beunfolded for import
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Hydrogen peroxide metabolism
Enzymes involved in the degradative oxidation (e.g., -oxidation of very
long chain fatty acids, 2-methyl-branched fatty acids, dicarboxylic acids,
leukotrienes, bile acid intermediates and cholesterol side chains, and both
a-andb-oxidation of 3-methyl-branched chain fatty acids);
The early steps in the synthesis of ether glycero-lipids orplasmalogens;
The formation ofbile acids, dolichol, and cholesterol; and
The catabolism of purines, polyamines, and amino acids, and the
detoxificationof reactive oxygen species such as hydrogen peroxide,superoxide anions, and epoxides. In methylotrophic yeasts, peroxisomes
are also involved in the metabolism of methanol and methyl amines.
Functions
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peroxisomal diseases
Genes mutation
proteinsinvolved
in the
uptakingMachinery
for
transport
Empty peroxisomes
Enzymes
fail to
be
imported
A single peroxisomal
enzyme absence
Defect in a
membrane protein
that transports VLCFAs
ALD: adrenoleukodystrophy ZS: Zellweger syndrome VLCFAs: Very-long-chain fatty acids
ZS
VLCFAs accumulate
in the brain
ALD
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Thank you
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Acknowledgement
Literature from internet
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I di V t i R h I tit t (IVRI) I t
PEROXISOMAL MATRIX PROTEIN IMPORT