04 neur cytol ma
TRANSCRIPT
![Page 1: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/1.jpg)
Neurocytology
Kandel
Chapter 4
Alberts,
Molecular Biology of the Cell,
Chapter 12
![Page 2: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/2.jpg)
Neurons resemble epithelial cell, except for their shape
![Page 3: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/3.jpg)
Organelles inside neurons are almost the same as in any other cell
Only plants
![Page 4: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/4.jpg)
• Neuronal structures:
– Nucleus– Cell body cytosol– Dendrites– Axon
Outside the nucleus:
• Ribosomes (CB and D)• Rough Endoplasmic Reticulum (CB and D)• Golgi complex (CB and D)• Lysosomes (CB and D)• Peroxisomes (CB and D)
• Mitochondria (CB, D and A)• Smooth Endoplasmic Reticulum (CB, D and A)
![Page 5: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/5.jpg)
The nucleus
has a double membrane with nuclear pores for the traffic of macromolecules:
Transcription factors and Nucleic acids
![Page 6: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/6.jpg)
Proteins are synthesized from mRNA synthesized in the nucleus and translocated to ribosomes
![Page 7: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/7.jpg)
A specific transport mechanism is responsible for mRNA traslocation
![Page 8: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/8.jpg)
An active transport system using GTP energy traslocates macromolecules in and out from the nucleus
![Page 9: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/9.jpg)
![Page 10: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/10.jpg)
Nuclear pores are typically made up by 8 subunits
![Page 11: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/11.jpg)
RIBOSOMES
Are produced in the nucleolus and transported to the extracllular space where some of them are taken by the endoplasmic reticulum (ER)
![Page 12: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/12.jpg)
Ribosomes are not organelles, in the sense that do not have an internal and external sides separated by a lipid membrane. They are made up by two subunits. Their total composition is 2/3 RNA and 1/3 proteins
![Page 13: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/13.jpg)
Complex mechanism of protein synthesis and folding
![Page 14: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/14.jpg)
Once they are in the extranuclear space part of the ribosomes stay free in the cytosol, and part of them stick to the Endoplasmic Reticulum (ER)
![Page 15: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/15.jpg)
The ER has two compartments: the “rough” ER and the “smooth” ER.
The rough ER is characterized by the presence of long lines of ribosomes that are continuously producing proteins and sending them to other organelles
Endoplasmic Reticulum
![Page 16: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/16.jpg)
Specific intracellular stimuli induce the release of Ca+2 from the ER
There are two separate Ca+2 stores:
1) IP3-gated
2) Ca+2-gated(Ryanodine-dependent)
Their activation transiently elevates [Ca+2]i, the cytosolic concentration of Ca+2
Another function of the Endoplasmic Reticulum:
![Page 17: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/17.jpg)
Ribosomes in Cell Body
and Dendrites
![Page 18: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/18.jpg)
![Page 19: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/19.jpg)
![Page 20: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/20.jpg)
Once proteins are synthesized and folded they detach from ribosomes but are not ready yet to function, and need to be properly folded and further modified
![Page 21: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/21.jpg)
Golgi apparatus
![Page 22: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/22.jpg)
Transmembrane protein can cross the membrane many times
![Page 23: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/23.jpg)
A series of enzymes starts to modify proteins when they are being synthesized (co-translational modifications)
![Page 24: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/24.jpg)
![Page 25: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/25.jpg)
Post-translational Modifications• Thioacylation - anchors to membrane– GAD, SNAP25, and GAP-43
• Isoprenylation - anchors to membrane– Ras and Rab GTPases
• Ubiquitin - Degradation • Glycosylation – NCAM
• Phosphorylation of Serine Threonine & Tyrosine
– Rapid modification of enzyme activity
Other modifications are performed after their synthesis
![Page 26: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/26.jpg)
Complex sugar chains are attached as a whole in the ER
![Page 27: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/27.jpg)
Lipids are attached sometimes to the end of the protein, as an anchor to the cell membrane lipid bilayer.Sugar-lipid chains characterize extracellular proteins like Ach-esterase or NCAM cell adhesion molecules
![Page 28: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/28.jpg)
Successive stages of further proteins modifications are performed in the Golgi apparatus, up to the transport of complete, functional proteins at their site of work
![Page 29: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/29.jpg)
Even after proper folding and posttranslational modification they are often not ready yet and need to be assembled in various subunits, like for instance many membrane channels
![Page 30: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/30.jpg)
DNA Protein
InactiveProtein
Inactive mRNA
Primary RNA
transcriptmRNAmRNA
1Transcriptional
Control
2RNA Processing
Control
4Translation
Control
5mRNA
DegradationControl
6Protein ActivityControl
3RNA Transport
Control
CytosolNucleus
![Page 31: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/31.jpg)
Gene expression can be controlled by regulating mRNA stabilityThe competition between mRNA translation and decay might be related to synaptic plasticity
![Page 32: 04 neur cytol ma](https://reader033.vdocuments.net/reader033/viewer/2022051400/55a4215f1a28aba9278b45fc/html5/thumbnails/32.jpg)