Pre-Medicine Program - Cell Export and Import
From CellBiology
Pre-Medicine Links
Biology 1 - Cell Types | Biology 2 - Cell Compartments, Membranes | Biology 3-4 - Cell Export/Import | Biology 5 Cell Cycle | Biology 7 - Cell Filament Systems | Biology 8 - Embryology
(https://php.med.unsw.edu.au/embryology/index.php?title=Pre-Medicine_Program_-_Embryology) | 2016 Note - These
are the 2015 lecture links and some content provided/replaced by other lecturers for 2016.
Cell Export - Exocytosis
Exocytosis and Endocytosis cartoon
Introduction
Cells make biological molecules (proteins), that carry out many different cell functions, and these
proteins are used within the cell or exported by a process called EXOCYTOSIS.
To make these biological molecules requires energy and the basic components, the cell imports
the materials it needs by a process called ENDOCYTOSIS.
The first lecture introduces how information is transferred from stable stored information (DNA)
converted to an intermediate (RNA) of variable stability, exported from the nucleus to the
cytoplasm where mRNA is then translated into Protein. This is gene expression, the products of
this process are used either within the cell, exported (exocytosis) or used to replace worn out
Dr Mark Hill
components. We will study this topic at the level of the cellular components and organelles
involved in the process: ribosomes, endoplasmic reticulum, Golgi apparatus, vesicles (transport and secretory). Movie Exocytic transport File:Exocytic transport.mov
The second lecture will introduce how substances are imported (endocytosis) and processed by the cell. There are a number of
processes by which the cell can absorb substances. The two main forms are by endocytosis or phagocytosis. Absorbed
substances include: substances required for cell growth, cell signaling toxic chemicals and drugs, bacteria and viruses. In
addition, this is also the main method for membrane removal and recycling.
Cell products and Signalling molecules are both exported from and imported into cell compartments using these processes.
Nutrients - Cells transport nutrients across cell membranes into specific compartments for cellular use.
For example - Insulin receptor, glucagon receptor and glucose transporter embedded in the plasma membrane.
Cell Secretion and Waste - Cells transport secretory products, signalling molecules and waste across cell membranes
into extracellular specific compartments.
For example - extracellular matrix, hormones, neurotransmitters are secreted by cells.
Part 1 Objectives
Brief understanding of gene expression
Understanding structure and function of organelles and structures associated with protein export (exocytosis)
ribosome, endoplasmic reticulum, vesicles - types and transport, Golgi apparatus structure and function
Brief understanding of transport between secretory compartments
Brief understanding of membrane turnover
Looking in the Cytoplasm
Difference between Prokaryotes and Eukaryotes
Light microscope - histology, immunohistochemistry - lacks details
within cytoplasmic compartment (Immunochemistry, Organelle
dyes, Fluorescent tagged proteins)
Electron microscope - shows the organelles and membrane structure
Links: MCB - The secretory pathway of protein synthesis and sorting
(http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=mcb.figgrp.4740) |
MCB - movie - Protein Secretion
(http://www.ncbi.nlm.nih.gov/books/bookres.fcgi/mcb/ch17anim2.mov) |
Play Movie - Exocytic transport | File:Exocytic transport.mov
Protein transport
The Cytosol
Cytosol membrane bound compartment
About 1/2 total cell volume
Intermediary metabolism takes place in the cytosol (Chemical
biological reactions, Degradation, Synthesis)
Protein molecules - cell has about 10 billion (1x1010) 10,000 to
20,000 different kinds
Compartments are Dynamic
Membrane bound compartments change shape and size
Related to cell cycle, differentiation, signaling
Eukaryotic Cell Physical Compartments
Links: MCB - Figure 17-1. Overview of sorting of nuclear-encoded
proteins in eukaryotic cells (http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=mcb.figgrp.4668) | MCoB Table 12-3. Some
Typical Signal Sequences (http://www.ncbi.nlm.nih.gov/books/NBK26907/table/A2150/?report=objectonly)
Ribosomes
1955 A small particulate component of the cytoplasm. PALADE GE. J Biophys Biochem Cytol. 1955 Jan;1(1):59-68.
PMID: 14381428 (http://www.ncbi.nlm.nih.gov/pubmed/14381428)
2009 The Nobel Prize in Chemistry 2009 (http://nobelprize.org/nobel_prizes/chemistry/laureates/2009/) awarded to Drs
Venkatraman Ramakrishnan, Thomas A. Steitz and Ada E. Yonath "for studies of the structure and function of the
ribosome".
Cartoon animation of translation on ribosome and export into endoplasmic reticulum
Ribosome Structure - Two ribosome types with identical structure (different locations - free and membrane bound), also
located within mitochondria. Free in cytoplasm Bound to endoplasmic reticulum
Ribosome Function - Protein Synthesis complexes where RNA sequences are converted to amino acid (aa) sequences
Codons 3 NTPs = 1 AA (AA incorporated at 20/sec, average sized protein takes 20-60 seconds to assemble)
Synthesis always in one direction and many ribosomes can bind 1 mRNA (polyribosome)
polyribosomes (polysomes are the EM visible granules), many ribosomes bound to a single mRNA
the synthesised single amino acid chain can then be "modified" in the cytoplasm or in specialised organelles
Play Movie - Ribosomes translating
Links: MBoC - Figure 1-10. A ribosome at work (http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=mboc4.figgrp.19) | MBoC
- Figure 12-37. Free and membrane-bound ribosomes (http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=mboc4.figgrp.2206) |
MBoC - Figure 6-63. A comparison of the structures of procaryotic and eucaryotic ribosomes
(http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=mboc4.figgrp.1073) |MCB - Model of protein synthesis on circular
polysomes and recycling of ribosomal subunits (http://www.ncbi.nlm.nih.gov/books/bv.fcgi?
highlight=movie&rid=mcb.figgrp.916) | MCB - movie ch4anim4.mov
(http://www.ncbi.nlm.nih.gov/books/bookres.fcgi/mcb/ch4anim4.mov)
Endoplasmic Reticulum
Ribosomes first EM
Nucleus and Rough Endoplasmic Reticulum
(tem)
Mammalian proteins transported into
endoplasmic reticulum
endoplasmic ‚"within the cell" and reticulum ‚ "a little net"
an organelle, membrane bound compartment within the cytoplasmic space
One structural compartment with two functional compartments
Rough Endoplasmic Reticulum (RER)
Smooth Endoplasmic Reticulum (SER)
Links: MBOC - The Endoplasmic Reticulum (http://www.ncbi.nlm.nih.gov:80/books/bv.fcgi?
db=Books&rid=mboc4.figgrp.2131)
Rough Endoplasmic Reticulum
Nucleus and RER tem
Function
Interphase ER tomography
Endoplasmic Reticulum
tubular domains
Protein Cellular Transport/Targeting
Mammalian proteins transported into er
Allows specific proteins to be modified and targeted to different destinations
Modification - amino acid chain cleaved and glycosylation = addition of carbohydrate (sugar) groups
Destination - Domestic (Cytosolic, Nuclear, Organelles) or Exported from cell
Structure
about 50% of total cell membrane and continuous with outer nuclear membrane
single highly convoluted membrane enclosing a single space (ER lumen = ER cisternae)
"rough" because of many ribosomes attached to the membrane, bound only to cytoplasmic side of ER membrane
Links: MBOC - The Endoplasmic Reticulum (http://www.ncbi.nlm.nih.gov:80/books/bv.fcgi?
db=Books&rid=mboc4.figgrp.2131) | MCB - Overview of sorting of nuclear-encoded proteins in eukaryotic cells
(http://www.ncbi.nlm.nih.gov/books/bv.fcgi?highlight=movie&rid=mcb.figgrp.4668) | MCB - movie - Protein Sorting
(http://www.ncbi.nlm.nih.gov/books/bookres.fcgi/mcb/ch17anim1.mov) JCB- movie - Real-time video of the formation of
tubules at ER export sites (http://www.jcb.org/cgi/content/full/152/1/213/F9/DC1)
Smooth Endoplasmic Reticulum (SER)
Smooth Endoplasmic Reticulum - Structure
Part of same membrane as RER (may also be called "transitional")
no attached ribosomes - not directly involved in protein synthesis
differ in shape - SER a meshwork of fine tubules
Smooth Endoplasmic Reticulum - Function
lipid metabolism (membrane)
carbohydrate metabolism
detoxification of drugs and harmful compounds
steroid synthesis and metabolism (cholesterol)
different amounts in different cells
In muscle cells - SER stores and releases calcium to trigger muscle
contractions.
Smooth Endoplasmic Reticulum
(Movie: RER to Golgi)
Links: MBoC - Transport from the ER through the Golgi Apparatus (http://www.ncbi.nlm.nih.gov/books/bv.fcgi?
rid=mboc4.section.2333)
Transport Vesicles
RER synthesized material is transferred by budding off of membrane
Forms transport vesicle - transports substances to different cellular locations
Most transport to Golgi apparatus by active transport mainly along microtubules (cytoskeleton, covered in next lecture)
Links: MBoC - Vesicular Traffic (http://www.ncbi.nlm.nih.gov/books/NBK21045/) | JCB - movie - transport vesicles and lipid
(http://www.jcb.org/cgi/content/full/153/3/529/F3/DC2) (large 9.7 Mb)
Golgi Apparatus
Golgi Apparatus - History
Discovered over 100 years ago by Camillo Golgi (1898) - seen in
neurons as anastomosing threads "internal reticular apparatus" and
soon detected in many cells..
Links: Nobel Prize 1906 Camillo Golgi, Santiago Ramon y Cajal
(http://www.nobelprize.org/nobel_prizes/medicine/laureates/1906/) |
MBOC - Golgi Apparatus- Summary
(http://www.ncbi.nlm.nih.gov:80/books/bv.fcgi?
Camillo Golgi
tool=bookshelf&call=bv.View..ShowSection&searchterm=golgi&rid=cell.section.d1e56569#d1e57172)
Golgi Apparatus - Structure
organelle, membrane enclosed structural compartment
cell may contain one or more Golgi apparatus
located near the nucleus
disc shaped membrane stack with different regions by their location within the cell
Golgi stack
from 6-30/stack
3-100s stacks/cell
many sets of membrane bound smooth
Stack Nomenclature
cis - bottom of stack closest to endoplasmic reticulum, receives
transport vesicles from ER
medial - middle of stack, processing of proteins, modification of
sidechains
surfaced cisternae
trans - top of stack closest to plasma membrane, buds off secretory
vesicles
Links: MBoC - Golgi Apparatus (http://www.ncbi.nlm.nih.gov:80/books/bv.fcgi?db=Books&rid=mboc4.figgrp.2347) | MBoC
- Figure 13-30. Two possible models explaining the organization of the Golgi apparatus and the transport of proteins from one
cisterna to the next (http://www.ncbi.nlm.nih.gov:80/books/bv.fcgi?db=Books&rid=mboc4.figgrp.2360) | MCB - Figure 5-49.
Three-dimensional model of the Golgi complex built by analyzing micrographs of serial sections through a secretory cell
(http://www.ncbi.nlm.nih.gov/books/bv.fcgi?highlight=golgi%20apparatus&rid=mcb.figgrp.1200)
Golgi Apparatus - Functions
Sorting of cytosolic/secreted proteins
Glycosylation of secreted proteins (adding carbohydrates or
"sugars"), Modification of carbohydrates, Side chains are also
trimmed
Trans vesicles fuse with the plasma membrane and secrete contents
from cell
Secretory Vesicles
Post-Golgi transport
protein export (secretion) by 2 forms constitutive and regulated
related also to membrane turnover - new lipid, new cholesterol and
new membrane proteins
Movies JCB - movie - transport vesicles and lipid
(http://www.jcb.org/cgi/content/full/153/3/529/F3/DC2) (large 9.7 Mb) |
JCB - movie - View of many Carriers
(http://www.jcb.org/cgi/content/full/149/1/23/F2/DC1)
Links: JCB - movie - View of many Carriers
(http://www.jcb.org/cgi/content/full/149/1/23/F2/DC1) (2.2 Mb) | JCB movie - Insulin Secretion
(http://www.jcb.org/cgi/content/full/jcb.200312033/DC1/1) (3.4 Mb) | JCB
- movie - transport vesicles and lipid
(http://www.jcb.org/cgi/content/full/153/3/529/F3/DC2) (9.7 Mb) |
Exocytosis types
Abnormalities - accumulation of abnormal proteins: misdirected (wrong "postcode"), truncated or altered modification
(missing enzymes)
Links: NCBI - Genes and Diseases (http://www.ncbi.nlm.nih.gov/books/bookres.fcgi/gnd/tocstatic.html) | NCBI - OMIM
(http://www.ncbi.nlm.nih.gov/sites/entrez?db=omim) |
Cell Import - Endocytosis
This second lecture introduces how substances that are imported (endocytosis) and processed by the cell.
There are a number of processes by which the cell can absorb substances. The two main forms are by endocytosis or
phagocytosis. Absorbed substances include: substances required for cell growth, cell signaling toxic chemicals and drugs,
bacteria and viruses. In addition, this is the main method for membrane removal and recycling.
We will study this topic at the level of the cellular components and organelles involved in the process: endosomes, lysosomes,
peroxisomes, transport vesicles, Golgi apparatus and endoplasmic reticulum.
Play Movie - Vesicles Display Bidirectional Motility along Microtubules | File:JCB200109030.v2.mov
Play Movie - Labelled Endosomes | File:Membrane label and endosomes.mov
Part 2 Objectives
Understanding of the function of endocytosis
Understanding structure of associated organelles: endosomes, lysosomes, peroxisomes, Golgi apparatus and
endoplasmic reticulum
Brief understanding of other cell import mechanisms, phagocytosis etc.
Brief understanding of signal, viral and bacterial entry into the cell
Brief understanding of transport within the cell
Cell Fractionation Techniques
Centrifugation generated 4 fractions: Nuclear, Mitochondrial, Microsomal and a Supernatant
History - 1974 Nobel Prize
Albert Claude - electron microscope for the study of animal cells and for development of differential centrifugation
George Palade - methodological improvements both differential centrifugation and electron microscopy, discovered and
described small granular components now known as ribosomes
Christian de Duve - identification of the isolated components which
were named lysosomes
Links: MBOC - Cell fractionation by centrifugation
(http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=mboc4.figgrp.1525) |
1974 Nobel Prize
(http://nobelprize.org/nobel_prizes/medicine/laureates/1974/index.html)
Cytosolic Vesicles
Single membrane bound vesicles
two membrane processes involved in trafficking: budding and
fusion
Linked to the ER and Golgi membrane system (lysosomes,
peroxisomes)
Endocytosis types
Endocytosis
Membrane compartments
Golgi Apparatus (electron microscope)
Peroxisomes
organelles that metabolize fatty acids, increased activity of digestion
in enzyme studies
Enzymes are Catalases (EC 1.11.1.6) - haem-containing proteins that
catalyse conversion of hydrogen peroxide (H2O2) to water and
molecular oxygen
Links: MBOC - EM Peroxisomes |
[http://www.ncbi.nlm.nih.gov:80/books/bv.fcgi?rid=mboc4.figgrp.2198
MBOC - EM Plant Peroxisomes
(http://www.ncbi.nlm.nih.gov:80/books/bv.fcgi?rid=mboc4.figgrp.2195) |
MBOC - Peroxisomes (http://www.ncbi.nlm.nih.gov:80/books/bv.fcgi?
db=Books&rid=mboc4.section.2194) | The Cell - Peroxisomes
(http://www.ncbi.nlm.nih.gov:80/books/bv.fcgi?
db=Books&rid=cooper.section.1676)
Absorption Mechanisms
Peroxisome
Phagocytosis
Receptor Mediated
Pinocytosis
“cell eating”
Endocytosis
occurs only in specialized cells macrophages,
dendritic cells and neutrophils
"cell drinking"
General term for all
capture and destroy pathogens and particulate
All cells, extracellular
mechanisms of absorbtion
antigens
fluid
extracellular fluid and
essential component of the innate immune response
micropinocytosis within
substances
Fc- and complement-receptor mediated
vesicles (<0.1 µm
substances bind to receptor
phagocytosis, named for binding specificity for
diameter)
sites
antibody tail region called Fc (Fragment,
macropinocytosis within
vesicle called endosome
crystallizable)
vacuoles (0.5-5.0 µm)
can be utilized by viruses to
clearance of apoptotic bodies
named macropinosomes
enter cells
some bacteria "hijack" this process in nonphagocytic cells to enter and infect them
Phagocytosis Phagocytosis Movie Neutrophil chasing Bacteria, remember this movie from the first lecture, where the white
blood cell chases and phagocytoses a bacteria in a blood smear.
Links: NRG - The role of the endosomal–lysosomal apparatus
(http://www.nature.com/nrg/journal/v3/n12/box/nrg963_BX1.html) | MBOC - Mechanisms used by bacteria to induce
phagocytosis by nonphagocytic host cells (http://www.ncbi.nlm.nih.gov/books/bv.fcgi?
highlight=movie&rid=mboc4.figgrp.4652) |
Endosome
Endosomes-GFP (http://tools.invitrogen.com/content/sfs/gallery/high/O10104_BP56_0808.jpg)
vesicle formed from plasma membrane budding that encloses extracellular fluid and substances
large ones called a "phagosome" or "vacuole"
Link: Insulin Degradation Model (http://edrv.endojournals.org/content/19/5/608/F1.expansion.html)
Lysosomes
The Cell - Endocytosis and lysosome formation (http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?
book=cooper&part=A1519&rendertype=figure&id=A1524)
Site of cellular digestion- contain up to 40 enzymes for digestion (the cell stomach)
Acid Hydrolases - active at acid pH (5), internal acidic environment
Lysosome Digestive Enzymes
enzymes named on basis of substrate
Protease - digests proteins
Nuclease - digests neucleotides (DNA)
Glycosidase - digests carbohydrates (sugars)
Lipases - digests lipids (fats)
Phospholipases - digests phospholipids (membranes)
Phosphatases - removes a phosphate group
Lysosome Types
Primary
newly formed without digestive
substrate
formed from budding Golgi
apparatus, can be secreted by
exocytosis
Secondary
active form enzyme + substrate
formed by vesicle fusion event
Lysosomes primary and
secondary
Links: ASCB - Lysosome History Series: 5. Historic Examples of Primary
Lysosomes (http://cellimages.ascb.org/cdm4/item_viewer.php?
CISOROOT=/p4041coll12&CISOPTR=95) | NRG - The role of the
endosomal - lysosomal apparatus
(http://www.nature.com/nrg/journal/v3/n12/box/nrg963_BX1.html)
Transport Vesicles
RER synthesized material is transferred by budding off of
membrane, forms transport vesicle
Transports substances to different cellular locations - Most transport
to Golgi apparatus
Active microtubule-based transport and also may use microfilament
transport
Endosomes
Endoplasmic Reticulum and Golgi
Both these systems involved with cell import and export
New proteins synthesized on membrane-bound ribosomes are transported through the Golgi apparatus
reach the trans-Golgi network (TGN) and sorted for delivery to various destinations
The question is how these compartments "sort" components going in different directions?
biodigested products from the digestive lysosomal pathway need now to be delivered to the biosynthetic pathway
amino acids, nucleotides, carbohydrates, phospholipids, lipids, etc
Endocytic Transgolgi Network (TGN)
By this stage you should now be able to fully label this figure
Some Other Vesicles
Synaptic Vesicles - secreted vesicle, neuron specific, filled with neurotransmitter
Melanosomes - membrane vesicle enclosing melanin (a light-absorbing pigment) protects agains DNA damage. Skin
melanocytes and retinal pigment epithelium cells, colour due to melanocytes level of activity not to the number of
melanocytes.
References
Science Lectures: Cell Export - Exocytosis | Cell Import - Endocytosis
Retrieved from "https://cellbiology.med.unsw.edu.au/cellbiology/index.php?title=Pre-Medicine_Program__Cell_Export_and_Import&oldid=75117"
Category: Exocytosis
This page was last modified on 1 December 2016, at 10:43.