1. Golgi Apparatus & Lysosomes
Lecture 21 BSCI 420/421 Oct 21/22, 2002
“It takes all the running you can do to stay in one place;
to get somewhere else, you must run twice as fast.”
-The Red Queen to Alice (In Wonderland)

2. The Golgi apparatus plays a central role in vesicular traffic
within cells; the post office of the eukaryotic cell.
Red=
foreward
Blue=
retrieval
Green=
endocytic
pathways

3. Proteins that reside in the ER lumen
can escape in a transport vesicle.
They are captured and returned by
KDEL receptors that bind a KDEL
sequence (lys-asp-glu-leu) on ER proteins.

4. The Golgi apparatus is an ordered series of compartments

5. TEMs of
Golgi
Apparatuses.
In an
animal
secretory cell
and
an algal cell
Chlamydomonas
(trans)
Note convex
cis face and
concave trans face.

6. Golgi Functions: A. Oligosaccharide processing
1. N-linked oligosaccharides can be trimmed back to a core
of 2 GlcNAc and 3 mannoses then extended to form a complex
oligosacc.
Or trimmed to a high mannose

7. This is done in a series of steps starting in the ER and
ending in the Golgi

8. Purposes?- 1. Sorting in TGN
2. Protection from protease digestion
3. Cell to cell adhesion via selectins (chap 19)

9. Cytochemical demonstration of different compartments of Golgi
Unstained nucleoside diphosphatase (cis)
Osmium Acid
Golgi Rxn phosphatase
(trans) (TGN)

10. Specific steps
of oligosacc.
processing
occur in
specific
compartments
2nd F(x)
Sorting of
proteins

11. Two alternative
Models to
explain the
transport of
proteins thru
the Golgi App.

12. Evidence:
Vesicular Transport
Panel 13-1.(study on your own)
In a cell free system, isolated Golgi apps can
exchange proteins by vesicular transport.
Proteins from mutant Golgi lacking GlcNAc transferase I
are able to have 3H-GlcNAc put on them by normal Golgi
in the same tube.
Cisternal Migration
Some structures too large to fit into transport vesicles
(collagen rods and algal scales) move progressively thru
Golgi stacks.
May be a combination of the two

13. Lysosomes are the sites of intracellular digestion.

14. Marking a lysosomal hydrolase with Mannose-6-P
Then the GlcNAc
is cleaved off,
leaving M6P
I-cell disease is due to a mutant GlcNAc Phosphotransferase

15. Transport of lysosomal enzymes to late endosomes,
which become lysosomes.