Myosin 5 Dependent Vesicle Trafficking

1
Myosin 5 Dependent Vesicle Trafficking
The Leonard Laboratory
2
Type II 5deiodinase

• Generates gt80 of the transcriptionally active T3
  in brain.
• Low serum T4 leads to a 10-fold increase in brain
  D2 levels due to slowed enzyme inactivation.
• T4 replacement lowers brain D2 levels by
  accelerating enzyme internalization along
  F-actin fibers.

3
Key Features about D2 biology

• D2 has a very short half-life in the cell (t½10
  min) due to rapid loss from the cell periphery.
• Microfilament disassembly prolongs the lifespan
  of D2 to 3 h. Microtubules are not required for
  the rapid loss of D2.
• The loss of D2 is accelerated by ligand-dependent
  interactions with F-actin fibers.

4
Ligand-dependent binding of D2 to F-actin
J. Biol. Chem.(2000) 275, 31701-31707
5
Lifecycle of type 2 deiodinase
6
Myosin Motor Proteins

• Head
• Actin binding
• Mg-ATPases
• Neck domain
• Light chain binding
• Variable length tail region
• Function
• Localization

7
Vesicle Trafficking Myosins

• Myosin I
• participate in growth cone formation, not
  associated with vesicles in the CNS.
• Myosins VI and VII
• play integral role in sensory cells (retina and
  stereocilia), no apparent role in central neurons
  and glia.
• Myosin V
• abundant in CNS and vesicle associated

8
Key features of the myosin 5a dimer
Vesicle docking
PEST
Tail
Coiled coil
Coiled coil
Neck
IQ
Motor
Head
9
Effects of the C-terminus of Myo5 on D2 Binding
to F-actin
J. Biol. Chem.(2000) 275, 31701-31707
10
The C-terminus of Myo5 shows Ligand-dependent
binding to endosomes
DMyoV
Control
T4
T4
11
VesicleF-Actin Binding Assay
Astrocytes
F-actin
p29GFP vesicles
Colchicine Rx
JBC 275, 31701-07, 2000
Mix
? ligand(s)
Triton spin
Triton supernatant
Triton pellet
12
Functional Domains of myo5
head
tail
head
myosinV
tail
AF-6
tail
1400
2800
4200
5600
1
endosome Bound
Nucleotide
truncation mutants
(mean se, n5)
--
100 15
CC
M
yoV
95 3
tail
Myo5a
18 11
1513
Myo5a
28 11
1767
Myo5a
2 2
1830
Myo5a
5 1
1803
Myo5a
87 12
Specific Antibody
coiled-coil
85 5
C-term
6 6
13
EFFECTS OF THYROID HORMONE OF VESICLE RECYCLING
IN CULTURED ASTROCYTES.
No hormone
T4
T3
14
No hormone
T4-treated
Myo5atail
1
2
5
N
N
4
3
P
P
P
P
P
P
P
P
P
P
1
2
3
4
5
15
10
1
8
3
6
5
N
7
2
4
9
16
(No Transcript)
17
Myo5atail
Myo5acoiled-coil
kDa
210
Myo5a
Myo5atail
97
69
IgG hc
45
30
Myo5acoiled-coil
18
-T4
T4
TRa1
TRa2
19
TRDa1 16 kDa
TRDa2 26 kDa
Amino acid sequence redrawn from Wagner, 1995.
Bars represent a helix (light grey) or b strand
(dark grey) underlined residues contact the TH
ligand.
20
TRa LBD (156-410)
H1
H2
S1
H1
H2
S1
156
qrpeptpeew
dlihvateah
rstnaqgshw
kqrrkflpdd
igqspivsmp
156
qrpeptpeew
dlihvateah
rstnaqgshw
kqrrkflpdd
igqspivsmp
H5
-
H6
H5
-
H6
H3
H4
H3
H4
FT
II
A
R
FT
II
A
R
206
dgdkvdleaf
se
k
tp
it
vvdfakk
lpmfselpce
dqiillkgcc
206
dgdkvdleaf
se
k
tp
it
vvdfakk
lpmfselpce
dqiillkgcc
TRDa LBD (Da1 256-410, Da2 256-453)
H5
-
H6
H7
H8
S2
S3
S4
H5
-
H6
H7
H8
S2
S3
S4
TRDa1 TRDa2
M
MS
RA
LS
L
GGL
I
M
MS
RA
LS
L
GGL
I
256
ei
l
av
rydpesdtlt
gemavkre
a
kn
gvv
sda
felgks
256
ei
l
av
rydpesdtlt
gemavkre
a
kn
gvv
sda
felgks
M
MS
RA
LS
L
GGL
I
M
MS
RA
LS
L
GGL
I
256
ei
l
av
rydpesdtlt
gemavkre
a
kn
gvv
sda
felgks
256
ei
l
av
rydpesdtlt
gemavkre
a
kn
gvv
sda
felgks
H9
H9
H10
H10
TRDa1 TRDa2
306
lsafnlddte
vallqavllm
stdrsgllcv
dkieksqeay
llafehyvnh
306
lsafnlddte
vallqavllm
stdrsgllcv
dkieksqeay
llafehyvnh
306
lsafnlddte
vallqavllm
stdrsgllcv
dkieksqeay
llafehyvnh
306
lsafnlddte
vallqavllm
stdrsgllcv
dkieksqeay
llafehyvnh
H12
H12
H11
H11
TRDa1 TRDa2
356
rkhniphfwp
migac
H
asrf
lh
M
kvecpte
lfppl
F
Levf edqev
356
rkhniphfwp
migac
H
asrf
lh
M
kvecpte
lfppl
F
kllmkvtdlr
kllmkerevq ssilykgaaa egrpggslgv hpegqqllgm
356
rkhniphfwp
356
rkhniphfwp
406 hvvqgpqvrq leqqlgeags lrgpvlqhqs
pkspqqrlle llhrsgi
TRDa2
21
Antibodies
anti-GFP
anti-TRa2
anti-TRa1
anti-myo 5atail
100
anti-myo 5acoil-coil
80
T4-dependent vesicle binding ( p29GFP bound)
60
40
20
0
Antibody dilution (fold)
100
22
MODEL OF LIGAND-DEPENDENT VESICLE DOCKING TO
MYOSIN 5