2009 Lecture 19

From CellBiology

Cell Signaling 1

This lecture is an introduction to a series of lectures on cell signaling. The first lecture is a general introduction to the different signaling mechanisms and the following two lectures look in detail at some specific examples of signaling pathways.

Note that you have already been introduced to signaling in many of your other lecture topics.

2008: ANAT3231 Lecture 18-19 Cell Signaling

Lecture Audio: Signal 1 Lecture Date: 19-05-2009 Lecture Time: 13:00 Venue: BioMed F Speaker: Mark Hill


  • Understand main types of signaling mechanisms
  • Understand concept of receptor and ligand
  • Understand membrane, cytoplasmic and nuclear receptors
  • Brief understanding of steroid hormone pathway
  • Brief understanding protein growth factor pathway
  • Understand differences between select membrane receptors (G protein structure, tyrosine kinases)

Lecture Summary

  • Messengers and Receptors
  • chemical signals
  • cellular receptors
  • signal transduction
  • intracellular pathways
  • second messengers
  • Examples of signaling

Signaling Mechanisms

MCB Movie - Extracellular Signaling

  • Endocrine
    • Hormone (at a distance)
  • Paracrine
    • Locally
  • Neurotransmitter
    • Specific form of paracrine
  • Autocrine
  • Local (self)
  • Contact Dependent

Cell Communication

  • Contact Mediated
    • display molecules on cell surface
    • recognized by receptor on another cell
  • Non-Contact Mediated
    • chemical signal
    • nearby or at a distance

Common Signals Signals and Receptors Signal Transduction Model Signaling between Tissues Regulation of cells and tissues

Hormones secreted by one tissue to regulate function of other cells or tissues

Chemical Signal Types

  • water soluble
  • lipid soluble

Movie: Hormone Signaling

Extracellular Signal Steps

  • Signaling Molecule
  • Synthesis
  • Release by signaling cell
  • Transport to target cell
  • Detection by a specific receptor protein
  • Change by receptor-signal complex (trigger)

Cell Surface Receptors

  • four main classes
    • G protein–coupled receptors
    • ion-channel receptors
    • receptors linked to cytosolic tyrosine kinases
    • receptors with intrinsic catalytic activity
  • ligand binding to cell-surface receptor
    • trigger intracellular pathways
    • modulate cellular metabolism, function, or development
  • Removal of the signal
    • often terminates cellular response

Second Messengers

cAMP molecular structure
Cyclic guanosine monophosphate (cGMP)
  • Cyclic nucleotides
    • cAMP, cGMP
  • Calcium Ions
  • Protein Kinase A
    • PKA, B, C
  • diacylglycerol (DAG)
    • modified lipid activates PKC
  • regulate the activity of cellular proteins
    • enzymes and non-enzymatic

Cell - Common intracellular signaling proteins

Steroid Responses

Steroid hormone receptor signaling


Cytosol location

  • receptor bound to inhibitor
  • ligand binding activates receptor
  • translocates to nucleus on ligand binding

Nuclear location

  • binds ligand and DNA
  • becomes transcription factor

MCB - Characteristic Properties of Principal Types of Mammalian Hormones | MCoB - Some signaling molecules that bind to nuclear receptors | Cell - Action of steroid hormones

Steroid Hormone Receptors (SHRs)

48 human nuclear receptor types

Steroid hormone receptor family
  • estrogen receptor, two forms ERα [NR3A1] and ERβ [NR3A2]
  • cortisol binding glucocorticoid receptor (GR) [NR3C1]
  • aldosterone binding mineralocorticoid receptor (MR) [NR3C2]
  • progesterone receptor (PR) [NR3C3]
  • dihydrotestosterone (DHT) binding androgen receptor (AR) [NR3C4]


Nuclear Receptor Signaling

Steroid Receptors

  • steroid binding region
  • near C-terminus
  • DNA binding
  • central region
  • zinc finger motif
  • alpha helix and 2 beta sheets held in place by cysteine or histidine residues by a zinc atom
  • multiple fingers typical
  • DNA response element
  • Enhancer


  • lipids acting as signaling molecules
  • act by binding to cell surface receptors
    • prostaglandins, prostacyclin, thromboxanes, and leukotrienes
  • rapidly broken down
  • act locally in autocrine or paracrine signaling pathways
  • synthesized from arachidonic acid



Essential Cell Biology

  • Essential Cell Biology Chapter 15

Molecular Biology of the Cell

Alberts, Bruce; Johnson, Alexander; Lewis, Julian; Raff, Martin; Roberts, Keith; Walter, Peter New York and London: Garland Science; c2002

Molecular Cell Biology

Lodish, Harvey; Berk, Arnold; Zipursky, S. Lawrence; Matsudaira, Paul; Baltimore, David; Darnell, James E. New York: W. H. Freeman & Co.; c1999

The Cell- A Molecular Approach

Cooper, Geoffrey M. Sunderland (MA): Sinauer Associates, Inc.; c2000

Search Online Textbooks



  • PubMed is a service of the U.S. National Library of Medicine that includes over 18 million citations from MEDLINE and other life science journals for biomedical articles back to 1948. PubMed includes links to full text articles and other related resources. PubMed
  • PubMed Central (PMC) is a free digital archive of biomedical and life sciences journal literature at the U.S. National Institutes of Health (NIH) in the National Library of Medicine (NLM) allowing all users free access to the material in PubMed Central. PMC
  • Online Mendelian Inheritance in Man (OMIM) is a comprehensive compendium of human genes and genetic phenotypes. The full-text, referenced overviews in OMIM contain information on all known mendelian disorders and over 12,000 genes. OMIM
  • Entrez is the integrated, text-based search and retrieval system used at NCBI for the major databases, including PubMed, Nucleotide and Protein Sequences, Protein Structures, Complete Genomes, Taxonomy, and others Entrez

Search Pubmed


  • The great divide: coordinating cell cycle events during bacterial growth and division. Haeusser DP, Levin PA. Curr Opin Microbiol. 2008 Apr;11(2):94-9. Epub 2008 Apr 7. Review. PMID: 18396093 | PMC
  • Cell cycle studies based upon quantitative image analysis. Stacey DW, Hitomi M. Cytometry A. 2008 Apr;73(4):270-8. Review. PMID: 18163464
  • Analysis of cell cycle phases and progression in cultured mammalian cells. Schorl C, Sedivy JM. Methods. 2007 Feb;41(2):143-50. Review. PMID: 17189856
  • Cell cycle regulation of DNA replication. Sclafani RA, Holzen TM. Annu Rev Genet. 2007;41:237-80. Review. PMID: 17630848



2009 Course Content


Cell Biology Introduction | Cells Eukaryotes and Prokaryotes | Cell Membranes and Compartments | Cell Nucleus | Cell Export - Exocytosis | Cell Import - Endocytosis | Cell Mitochondria | Cell Junctions | Cytoskeleton Introduction | Cytoskeleton 1 Intermediate Filaments | Cytoskeleton 2 Microtubules | Cytoskeleton 3 Microfilaments | Extracellular Matrix 1 | Extracellular Matrix 2 | Cell Cycle | Cell Division | Cell Death 1 | Cell Death 2 | Signal 1 | Signal 2 | Stem Cells | Stem Cells | Development | Revision


Introduction to Lab | Microscopy Methods | Preparation/Fixation | Immunochemistry | Cell Knockout Methods | Cytoskeleton Exercise | Confocal Microscopy | Tissue Culture 1 | Tissue Culture 2 | Microarray Lab visit

Dr Mark Hill 2015, UNSW Cell Biology - UNSW CRICOS Provider Code No. 00098G