Cellular Pathology_Growth Control

Cellular Pathology

Chapter 4. Tissue Repair: Cellular Growth,
Fibrosis, and Wound Healing

학습목적 세포의 신호전달체계를 이해함으로써 세포의 활동이 어떻게 조절되는지를 알고, 신호전달체계가 잘 못 되었을 때 어떤 일이 벌어질 수 있는가를 생각하며, 치유와 수복과정을 이해한다.

CONTROL OF NORMAL CELL GROWTH

Cell Cycle and Proliferative Potential

- Labile Cells

     : Continuously dividing cells

체세포를 재생능력에 따라 분류하고, 그 특성을 설명한다. (A)

     : Surface epithelia; Squamous, columnar,
                          transitional
       Hematopoietic, lymphoid, splenic tissue

- Stable cells

: Quiescent cells, dividing by stimulation

      : Parenchymal cells of glandular organs;
          Liver, kidney, pancreas
        Mesenchymal cells;
           Fibroblasts, endothelial cells, smooth muscle cells,            chondroblasts, osteoblasts,

    : The underlying framework of the parenchymal
      cells, mainly the basement membrane, is
      necessary for organized regeneration

regeneration re- + L. generare to produce, bring to life

- Permanent cells

: Nondividing cells in postnatal life

: Nerve cells
Skeletal and cardiac muscle cells, practically

Cell populations and cell cycle phases.

Constantly dividing labile cells continuously cycle from one mitosis to the next. Nondividing permanent cells have exited the cycle and are destined to die without further division. Quiescent stable cells in G₀ are neither cycling nor dying and can be induced to re-enter the cell cycle by an appropriate stimulus.

Molecular Events in Cell Growth - Biosignaling

Cell Signaling

Plasma membrane receptor의 종류를 열거한다. (A)

Plasma membrane receptors

            0. Ligand-gated ion channels
            1. Receptor enzymes
                 (1) TK receptors (Receptors with intrinsic kinase activity)
                 (2) Serine-threonine kinase receptor
                 (3) Guanylyl cyclase receptors
            2. Receptor non-enzymes (Cytokine receptor superfamily)
                 (1) JAK/STAT system
            3. G protein-linked receptors (Seven-spanning receptors,
                                           Serpentine receptors)

<Signal Transduction Pathway>

    I. Ligand-receptor binding, membranous

   II. Activation of receptors

  III. Signal transduction and second messengers

         1. Receptor enzymes

signal transduction pathway의 과정을 설명한다. (A)
G proteins = Guanine nucleotide-binding) proteins) with intrinsic GTPase activity

- Monomeric G
  proteins (ras)
- Heterotrimeric G
  proteins (Gαβγ)

(1) TK receptors (Receptors with intrinsic kinase activity) -
InsulinR, EGFR(c-erb B1), PDGFR, FGFR, VEGFR,AngiopoietinR

                     (a) MAP kinase pathway (ras pathway)
                     (b) PI-3-kinase pathway
                         (Phosphoinositide-3-kinase pathway)

                     (c) IP₃ pathway (Phospholipase C (PLCγ) pathway)
                           : PLCγ = IP3 - Ca⁺⁺ - Ca⁺⁺-binding proteins↑
                                   = DAG - PKC↑
                                    (Tumor promoter: Phorbol esters)
                     (d) src family pathway (with tyrosine kinase activity)

(2) Serine-threonine kinase receptor

(a) TGFβ receptor

(3) Guanylyl cyclase receptors

(a) ANP receptor, guanylin receptor
(b) NO receptor

2. Receptor non-enzymes (Cytokine receptor superfamily)

(1) JAK/STAT system: Cytokine receptors, leptin receptor

3. G protein-linked receptors (Seven-spanning receptors,
Serpentine receptors)

: Heterotrimeric G proteins (Gαβγ)

(1) cAMP pathway

                      - β-Adrenergic R., glucagon R., chemokine Rs.
                          : G_s- Adenylate cyclase - cAMP - PKA↑
                      - Somatostatin R.
                          : G_i- Adenylate cyclase↓ - cAMP↓ - PKA↓
                      - Gustatory R.
                          : G_gust- Adenylate cyclase - cAMP - PKA↑ - P_K+↓
                           (gustducin)                       (depolarization)
                      - Olfactory R.
                          : G_olf- Adenylate cyclase - cAMP - P_{Ca++, Na+}↑                                                             (depolarization)

cGMP pathway

                      - Photoreceptor (rhodopsin)
                          : Transducin - Phosphodiesterase-cGMP↓-P_{Ca++, Na+}↓
                                                          (hyperpolarization)

(2) IP₃ pathway (Phospholipase C (PLCβ) pathway)

                      - Olfactory R.
                          : G_olf - PLCβ - IP3 - P_Ca++↑ (depolarization)                      - Chemokine Rs.,
                        Acetylcholine [muscarinic M1] R.,
                        α1-adrenergic agonist R.
                          : Gq - PLCβ = IP3 - Ca⁺⁺ - Ca⁺⁺-binding proteins↑
                                       = DAG - PKC↑
                                        (Tumor promoter: Phorbol esters)

IV. Transcription factors

1. Early response genes

: c-fos, c-jun, c-myc

2. Late response genes

*. Phosphatases

: Phosphatase inhibitor - Tumor promoter: Okadoic acid

Signaling from activated tyrosine kinase receptors

(a) MAP-kinase pathway (ras pathway)      Binding of a growth factor causes the receptor to dimerize and cross-phosphorylate tyrosine residues. Binding of adapter (or bridging) proteins (e.g. GRB2 and SOS) couple the receptor with inactive Ras. Cycling of Ras between its inactive and active forms is regulated by GAP. Activated Ras interacts with and activates Raf-1. This kinase then phosphorylates a component of the MAPK signaling pathway, MEK, which then phosphorylates MAPK (ERK). Activated MAPK phosphorylates other cytoplasmic proteins and nuclear transcription factors generating cellular responses. The phosphorylated tyrosine kinase receptor can also bind other components, such as PI-3 kinase, which activates distinct signaling systems.

(b) PI-3-kinase pathway
    (Phosphoinositide-3-kinase pathway)

  Ligand - Tyrosine kinase receptor →

  PI-3-K (PI3-kinase = Phosphoinositide-3-kinase) →

  PIP₂ (phosphatidyl inositol bisphosphate) →
  PIP₃ (phosphatidyl inositol trisphosphate) →

  PKB (protein kinase B) →

  Phosphorylation of target proteins

(c) IP₃ pathway
    (Phospholipase C (PLCγ) pathway)

     Vide infra (Phospholipase C (PLCβ) pathway)

(d) src family pathway,
    with tyrosine kinase activity

ras pathway를 그림으로 설명한다. (A)

GRB2 = Growth factor Receptor Binding protein 2 with SH2 domain (Src Homology domain 2)
(Src = encoded by src gene of avian sarcoma virus)

SOS = son of sevenless = GNRP = Guanine nucleotide releasing protein

ras = rat sarcoma virus

GAPs = GTPase activating proteins

Raf-1 = Ras-activated factor 1

MEK = MAPK/ERK activating kinase

MAPK = Mitogen-Activated Protein Kinase = ERK (Extracellular signal-Regulated Kinase)

inositol G. is, (gen,) inos fiber, muscle finer, sinew + ISV -ite + -ol

PI-3-kinase pathway를 설명한다. (A)

PI-3-kinase = phospho-
inositide-3-kinase

PIP₂ = phosphatidyl inositol 4,5-bisphosphate

PIP₃ = phosphatidyl inositol 3,4,5-trisphosphate

PLCγ
    Phospholipase Cγ,
    with SH2 domain,
    activated by
    tyrosine kinase
    receptors

DAG = 1,2-diacyl glycerol

IP₃ = inositol 1,4,5-trisphosphate

PKC Ca⁺⁺-dependent
    protein kinase

* SOS (son of sevenless) = GNRP (Guanine nucleotide
releasing protein).

The eye of Drosphila is composed of about 800 identical units, each having a separate lens that focuses light onto eight photoreceptor cells at its base. R7 is the last photoreceptor cell to develop, required for the detection of UV light. A mutant fly with R7 defect is called sevenless (sev), and the gene sev. The sev gene is a receptor tyrosine kinase and requires a second gene, son-of sevenless (sos), to activate Ras. The sos gene encodes GNRP.

SEM of a compound eye of Drosophila.

Signaling from activated receptor non-enzymes

JAK/STAT system by which the leptin signal is transduced in the hypothalamus. Leptin binding induces dimerization of the leptin receptor, followed by phosphorylation of Tyr residues of the receptor, catalyzed by JAK. STATs that bind to the phosphorylated leptin ceceptor are then phosphorylated on Tyr residues by a separate activity of JAK. The STATs dimerize, binding each other's phosphorylated Tyr residues, and enter the nucleus, where they bind specific regulatory regions in the DNA and alter expression of specific genes. The products of these genes ultimately influence feeding behavior and energy expenditure.

JAK/STAT system을 그림으로 설명한다. (A)

JAKs = Janus kinases

STATs = signal transducers and activators of transcription

Signaling from activated guanylyl cyclase receptors

      (a)            (b)

Two types (isozymes) of guanylyl cyclase involved in signal transduction.

(a) ANF receptor, guanylin receptor
     The first type exists in two similar membrane-spanning forms that are activated by their extracellular ligands: ANF receptors (left) in cells of the renal collecting ducts and the smooth muscle of blood vessels and guanylin receptors (right) in intestinal epitethelial cells. The guanylin receptor is also the target of a bacterial endotoxin that triggers severe diarrhea.

(b) NO receptor
     The second type is a soluble enzyme that is activated by intracelluar NO; this form is found in many tissues, including smooth muscle of the heart and blood vessels.

ANF = atrial natriuretic factor

NO = nitric oxide

Signaling from activated G protein-linked receptors

(a) cAMP pathway, involving stimulatory G protein
(G_s)

cAMP pathway (G_s)를 그림으로 설명한다. (A)

cAMP

G_s = stimulatory G protein

PKA = cAMP-dependent protein kinase

(b) IP₃ pathway
    (Phospholipase C (PLCβ) pathway).     Binding of a ligand to a seven transmembrane receptor activates a G protein, which in turn activates phospholipase C. This enzyme then cleaves phosphatidylinositol 4,5-triphosphate (IP3) and 1,2-diacylglycerol (DAG). DAG activates protein kinase C, which phosphorylates a series of proteins altering cell function. The IP₃ diffuses through the cytoplasm and interacts with membrane channels in the endoplasmic reticulum, causing release of calcium ions and cellular responses.

IP₃ pathway (PLCβ)를 그림으로 설명한다. (A)

PLCβ
    Phospholipase Cβ,     activated by G
    protein

PKC Ca⁺⁺-dependent
    protein kinase

Activation of glucocorticoid receptors

* Estrogen antagonist: Tamoxifen
Progesterone antagonist: RU486

항암제 tamoxifen과 사후 피임제 RU486의 약리기전을 설명한다. (A)

Cell Cycle and Regulation of Cell Division

<Cell Cycle and Cyclins>

: Cdk-cyclin complexes

Cell cycle을 그림으로 설명하고 이를 제어하는 인자들을 기술한다. (B)

Cell cycle을 조절하는 molecule들을 어떻게 발견했을까?, 어떻게 이름 지었을까 ☞

Growth Factors

<Classification>

    1. Growth stimulators (Growth factors)

대표적인 growth factor들과 이들의 역할을 기술한다. (B)

         = Competence factors: Rendering the cells
             competent to do DNA synthesis

         = Progression factors: Stimulating DNA
             synthesis in competent cells

Growth factor와 oncgene과의 관계 ☞

2. Growth inhibitors

          : Transforming growth factor β
            Tumor necrosis factor
            Interferon β

3. Factors for cell locomotion, contractility, and differentiation

- Epidermal growth factor (EGF)

         : Proliferation of epithelial cells and fibroblasts
         : EGF-EGFR tyrosine kinase (c-erb B1) →
           Phosphorylation →
           RNA and DNA synthesis

Transforming growth factor alpha (TGFα)

: Homology to EGF

- Platelet-derived growth factor (PDGF)

          : Platelets (α granules)
            Macrophages, endothelial cells, smooth muscle cells,
            tumor cells
          : Migration and proliferation of fibroblasts,
            smooth muscles, and monocytes
          : PDGF-PDGFR tyrosine kinase

- Fibroblast growth factor (FGF)

= Acidic FGF (aFGF, FGF-1)
= Basic FGF (bFGF, FGF-2): Angiogenesis

: Multifunctional
: FGF-FGFR tyrosine kinase

- Vascular endothelial growth factor (VEGF) = Vascular permeability factor

: Vasculogenesis
Angiogenesis

- Transforming growth factor beta (TGFβ)

          : Platelets, endothelial cells, lymphocytes, macrophages
          : Growth inhibitor/stimulator
            Fibrogenesis
            Deactivation of macrophages
          : Serine-threonine kinase receptor

- Cytokines - IL-1 and TNF

: Fibrosis and remodelling of connective tissue

EXTRACELLULAR MATRIX AND CELL-MATRIX INTERACTIONS

* EXTRACELLULAR MATRIX

Extracellular matrix의 구성성분을 열거한다. (A)

- Structural fibrous proteins

= Collagen: Strengthened organization
= Elastin: Resilience

- Adhesive glycoproteins

         = Fibronectin
             : Heterodimer
               Mesenchymal cell-matrix attachment via integrin and RGD
         = Laminin
             : Heterotrimer, cross-shaped
               Epithelial cell-basal lamina attachemnt
         = Nonfibrillar collagen
         = Thrombospondins
         = Tenascin

     - Polysaccharides and proteoglycans (Ground substances)

        = Glycosaminoglycans (Mucopolysaccharides)

            : Hyaluronic acid (hyaluronan)

glycan polysaccharide

= Proteoglycans (Mucoproteins)

             : Core protein + Glycosaminoglycans
                                - Chondroitin sulfate,
                                  dermatan sulfate
                                - Heparan sulfate, heparin
                                - Keratan sulfate

<Organization of ECM>

Extracellular matrix의 organization을 열거한다. (A)

- Interstitial matrix

- Basement membrane

         = Type IV collagen
         = Fibronectin
         = Laminin
         = Proteoglycans
         = Others


monomer	dimer		meshwork

Basement Membrane - Type IV Collagen

<Cell-Matrix Interactions>

Cell과 Extracellular matrix의 interaction을 열거한다. (A)

- Integrins

         : Integrins on cell ↔ RGD of Fibronectin, laminin, collagen in ECM,
           forming focal adhesion complexes and providing tensegrity
         : Cell proliferation, differentiation, locomotion

- Cell surface proteoglycans

= Syndecan ↔ Fibronectin, collagen, thrombospondin in ECM

- Matricellular proteins

         : Secreted adaptor proteins between cells and ECM
         = SPARC (secreted protein acidic and rich in cysteine) (= Osteonectin)
         = Osteopontin
         = Thrombospondins
         = Tenascin

Schematic illustration of the sequence of events in the invasion of epithelial basement membranes by tumors (A-C). Tumor cells attach to the basement membrane via the laminin receptors and secrete proteolytic enzymes, including type IV collagenase and plasminogen activator. Degradation of the basement menbranes and tumor cell migration follow.