Psy 111 Basic concepts in Biopsychology

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• Psy 111 Basic concepts in Biopsychology
• Lecture 2 Cells and their Proteins

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Lecture Objectives

• Describe the major functions of the cells of the
  nervous system neurons and glia.
• Describe the different parts of a neuron and
  define the concept of compartmentalization.
• Describe the structure and role of the cellular
  membrane and cytoskeleton.
• Identify the basic functions of mitochrondira,
  the nucleus, endoplasmic reticulum, and Golgi
  apparatus.
• Describe the dogma of gene expression and the
  protein synthesis machinery common to all cells.
• Describe transcription and the mechanisms of
  its regulation with emphasis of the importance of
  chromatin remodelling.
• Describe translation and the mechanisms of its
  regulation and discuss RNA silencing.
• Describe post-translational processing and where
  it occurs.
• Describe protein transport within the neuron.

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Cellular Components of the Nervous System

• Cells of the nervous system
• Parts of a cell
• Protein synthesis a.k.a. gene expression

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Cells of the Nervous system

• Nervous system is made up of 100s of billions of
  cells
• Only 10 of them are neurons!

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Cells of the Nervous System
I. Neurons cells that are capable of sending
and receiving chemical signals and to transmit
information from place to place (along the cell)
with electrical signals
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Types of Neurons
Classification on Type of Connections Class
- afferent/sensory - efferent/motor
-interneuron
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Morphology number or length of processes

• Multipolar- motor neurons
• Unipolar-sensory neurons
• Bipolar-sensory neurons
• Interneurons-in spinal cord and brain
• Polarity refers to the number of processes
  coming from the cell body (dendrites and axon)

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Types of Neurons
Classification on Neurotransmitters -Chemical
amino acids, monamines, peptides,
etc -Function inhibitory, excitatory,
modulatory
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The Glia
Types of glia cells

• Myelin producing glial cells
• Oligodendrocytes (CNS)
• Schwann cells (PNS)
• Astrocytes largest glia, star-shaped
• Involve in various functions that support neurons
• Involved in information processing
• Microglia Immune response and removal of debris

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Astrocytes
Neurons
Blood vessel
Brain tissue stained for an astrocyte marker
(Glial Fibrial Acidic Protein - only found in
astrocytes)
Astrocytes
Hold the neurons in place (Glia glue) and
isolate them -assist in the transfer of
chemicals (nutrients and waste products) from the
blood to the nervous system wrap around blood
vessels -also take up and release ions,
neurotransmitters. ?may be key players in
neurotransmission.
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Cellular Components of the Nervous System

• Cells of the nervous system
• Parts of a cell
• Protein synthesis a.k.a. gene expression

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Parts of the Neuron compartmentalization
functional segregation.
Dendrites input Body protein
production Initial Segment integration Axon
conduction Terminal output
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Microstructure of Soma/Cell Body
-compartmentalization -specialization of cellular
components
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Cell (or Plasma) Membrane
Cells live in an aqueous (water-based)
environment but require ability to maintain a
desired internal state. This requires a barrier
to outside of cell which is achieved by the cell
membrane -gt defines intra- vs. extra-cellular
spaces.
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Cellular membrane
Phospholipid bilayer.
Hydophillic-interacts with water/environment
Hydophobic -barrier to water.
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Cellular membrane
Proteins receptors channels
pumps enzymes

• Membrane plays a critical role in communication
  between cells.
• An important aspect of the membrane is that it is
  dynamic protein components change and move
  around critical for neuroadaptations.

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Cytoplasm
Aqueous solution (cytosol) Organelles
Cytoplasm comprises the area between the plasma
membrane and the nucleus which includes cytosol
(aqueous environment) and cellular organelles.
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Cytoskeleton
-allows localization and interconnection between
organelles. -give shape to neurons or glia
dynamically modulated ? role in the plasticity of
neurons.
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Mitochondria cells power house.
Cellular Energy
Structure Rod- or oval-shaped body surrounded by
two membranes. Inner membrane folds into matrix
of the mitochondrion, forming cristae. Functions
Major site of ATP production, O2 utilization, and
CO2 formation. Contains enzymes of Krebs cycle
and oxidative phosphorylation.
Double membranes contains metabolic
proteins Metabolic enzymes provide usable
energy for cell
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Nucleus
Chromosomes store genetic info (DNA) Nucleolus
production of RNA
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Endoplasmic Reticulum Rough vs.
Smooth
Membranes Enzymes Ca store
Membranes Ribosomes (enzyme complex)
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Golgi Apparatus
Membranes Enzymes
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Basic Cellular Components of the Nervous System

• Cells of the nervous system
• Parts of a cell
• Protein synthesis a.k.a. gene expression

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Compartmentalization
Dendrites input Body protein
production Initial Segment integration Axon
conduction Terminal output
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Protein Synthesis Cell Differentiation/Specializ
ation

• All cells of an organism share the same genes
  (DNA).
• But cell can perform different biological
  function through selective expression of DNA/
  synthesis of protein

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Gene Expression Protein Synthesis
Gene Expresion DNA mRNA Protein
The end result of gene expression is a specific
protein that contributes to the function of the
cell.
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Transcription
DNA -gt mRNA
-only sense or template DNA is transcribed to
RNA. -RNA is complementary to template DNA
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Allows -Multiple versions of same gene.
-Multiple products to be co-transcribed.
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-end result of some forms of neuronal
communication, hormone actions, target of drug
action
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Epigenetics/Chromatin Remodeling DNA Methylation
Addition of methyl groups to nucleotides of DNA
(at CpG) will reduce transcription of the gene.
This type of change is typically permanent due to
maintenance enzymes (e.g. Dnmt1) and initially
thought to only occur in the development but
recently it has been shown to be produced by
learning and drug exposure
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Epigenetics/Chromatin Remodeling Histone
modifications
?Acetylation ?Methylation ?Trascription
?Acetylation ?Methylation ?Trascription
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EpigeneticsChromatin Remodeling Histone
Modifications

• Addition of acetyl groups to histones will
  facilitate transcription of the gene.
• Histone Acetyltransferase (HAT) adds acetyl group
  to histone.
• Histone deacetylase (HDAC) removes acetyl group.
• Addition (HMT) or removal (HDM) of methyl groups
  to specific histones also modulates
  transcription.

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Protein Synthesis Cell Differentiation/Specializ
ation

• All cells of an organism share the same genes
• But cell can perform different biological
  function through selective protein expression
• Much of the cell-type specific gene expression is
  controlled by epigenetic mechanisms.

But back to our mRNA
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mRNA Transported to Cyoplasm
Specialized chaperone proteins serve to bring
mRNA out of nucleus to the cytoplasm ensure
other molecules do not enter or exit nucleus.
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Translation on Ribosomes
mRNA -gt polypeptide (pre-protein)
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rER versus Free Ribosomes
rER -gt encapsulated proteins proteins
destined to be membrane-bound proteins destined
to be secreteted
Free ribosomes Cytoplasmic proteins Nuclear
and mitochondrial roteins
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Coding of Genetic Information Codons
Condon functional unit of DNA (RNA) code 3
nucleotides
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Peptide Bonds
Proteins (or polypeptides) are comprised of 2 -
1000s of amino acids joined together via a
common method
Each linage between amino acids is formed by a
peptide bond in a sequential fashion -ribosome
is specialized enzyme complex for making peptide
bonds between AAs with the sequence of AAs
determined by mRNA. -gtProduct of ribosome is a
poly-peptide pre-protein.
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Blocking TranslationRNA Silencing/Interference

• RNA silencing/interference a short strand of RNA
  can bind to a complimentary segment of the mRNA
  to block translation.
• The inhibiting strand is referred to as
  micro-RNA (miRNA) if it is endogenously
  produced.
• The inhibiting strand is referred to as short
  hairpin loop-RNA (shRNA) if it is artificially
  produced.

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Post-translational Processing
Golgi Apparatus Cleavage into smaller
polypeptides
N.B. this should refer to polypeptides because
only end functional product is a protein.
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Post-translational Processing
Golgi Apparatus can Glycosylation addition
of sugars (carbohydrates). Phospholipidation
addition of fats.
Translation on rER
Modification and packaging into vesicle
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Post-translational Processing
Once the final polypeptide is derived needs to
take on proper conformation or shape may
involve multiple polypeptides working together.
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Summary of Protein Synthesis
1. Transcription
2. Translation

• Post-translational processing trafficking