CSIR-NET LIFE SCIENCES

Unit 4: Cell Communication and Cell Signaling

Complete Topic-Wise Syllabus

Cell Signaling • Cellular Communication • Immunology • Host–Pathogen Interaction • Cancer Biology

A. Cell Signaling

📡 1. General Principles of Cell Signaling

• Cell-to-cell communication
• Signal generation
• Signal reception
• Signal transduction
• Cellular response
• Signal amplification
• Signal termination
• Short-range signaling
• Long-range signaling

🧪 2. Types of Signaling

• Endocrine signaling
• Paracrine signaling
• Autocrine signaling
• Juxtacrine signaling
• Synaptic signaling
• Contact-dependent signaling

🧬 3. Hormones and Their Receptors

• Peptide hormones
• Steroid hormones
• Amino acid-derived hormones
• Cell-surface hormone receptors
• Intracellular hormone receptors
• Nuclear receptors
• Hormone-receptor specificity

📲 4. Cell Surface Receptors

• G-protein coupled receptors
• Receptor tyrosine kinases
• Cytokine receptors
• Serine/threonine kinase receptors
• Ion channel-linked receptors
• Integrin receptors

🔄 5. G-Protein Coupled Receptors (GPCRs)

• Seven-transmembrane receptor structure
• Heterotrimeric G-proteins
• Gα, Gβ and Gγ subunits
• GDP-GTP exchange
• G-protein activation
• GTP hydrolysis
• Gs proteins
• Gi proteins
• Gq proteins

⚡ 6. GPCR Signaling Pathways

• Adenylyl cyclase pathway
• cAMP
• Protein kinase A
• Phospholipase C pathway
• IP₃
• DAG
• Protein kinase C
• Intracellular Ca²⁺

🧪 7. Second Messengers

• cAMP
• cGMP
• IP₃
• DAG
• Ca²⁺
• Nitric oxide
• Signal amplification

🧬 8. Major Signal Transduction Pathways

• Ras-Raf-MEK-ERK pathway
• MAP kinase pathway
• PI3K-Akt pathway
• JAK-STAT pathway
• NF-κB pathway
• Wnt signaling pathway
• Notch signaling
• Hedgehog signaling
• TGF-β signaling

🔬 9. Regulation of Signaling Pathways

• Receptor desensitization
• Receptor internalization
• Phosphatases
• Feedback inhibition
• Signal termination
• Protein degradation
• Second messenger degradation

🦠 10. Bacterial Two-Component Systems

• Sensor kinase
• Response regulator
• Histidine phosphorylation
• Signal perception
• Phosphotransfer
• Transcriptional response

🌱 11. Plant Two-Component Systems

• Plant histidine kinases
• Response regulators
• Cytokinin signaling
• Phosphorelay system
• Plant hormone signaling

☀️ 12. Light Signaling in Plants

• Photoreceptors
• Phytochromes
• Cryptochromes
• Phototropins
• UV receptors
• Light-dependent gene expression
• Photomorphogenesis

🧭 13. Bacterial Chemotaxis

• Chemotactic receptors
• Methyl-accepting chemotaxis proteins
• Che proteins
• Flagellar movement
• Run and tumble behavior
• Chemical gradient sensing

🦠 14. Quorum Sensing

• Cell-density-dependent signaling
• Autoinducers
• Quorum sensing in Gram-negative bacteria
• Quorum sensing in Gram-positive bacteria
• Biofilm formation
• Virulence regulation
• Bioluminescence

🎯 CSIR-NET High-Yield:
GPCR → G-protein → Adenylyl cyclase → cAMP → PKA
GPCR → Gq → PLC → IP₃ + DAG → Ca²⁺ + PKC
RTK → Ras → MAPK pathway
Cytokine receptor → JAK → STAT

B. Cellular Communication

📡 1. General Principles of Cell Communication

• Cell recognition
• Cell adhesion
• Cell signaling
• Cell-cell interaction
• Cell-matrix interaction
• Signal integration

🔗 2. Cell Adhesion Molecules

• Cadherins
• Integrins
• Selectins
• Immunoglobulin superfamily CAMs
• Cell-cell adhesion
• Cell-matrix adhesion

🔗 3. Cell Junctions

• Tight junctions
• Adherens junctions
• Desmosomes
• Hemidesmosomes
• Gap junctions

🕳️ 4. Gap Junctions

• Connexins
• Connexons
• Intercellular channels
• Small molecule exchange
• Electrical coupling
• Calcium signaling

🧱 5. Extracellular Matrix

• Collagen
• Elastin
• Fibronectin
• Laminin
• Proteoglycans
• Glycosaminoglycans
• Basement membrane

🔗 6. Integrins

• Integrin structure
• α and β subunits
• Cell-matrix attachment
• Bidirectional signaling
• Outside-in signaling
• Inside-out signaling
• Integrin-mediated migration

🧠 7. Neurotransmission

• Neurons and synapses
• Presynaptic terminal
• Synaptic vesicles
• Neurotransmitter release
• Calcium-dependent exocytosis
• Postsynaptic receptors
• Excitatory neurotransmission
• Inhibitory neurotransmission

⚡ 8. Regulation of Neurotransmission

• Action potential
• Voltage-gated Ca²⁺ channels
• SNARE proteins
• Neurotransmitter release
• Reuptake
• Enzymatic degradation
• Presynaptic regulation
• Postsynaptic regulation

🩸 9. Regulation of Haematopoiesis

• Hematopoietic stem cells
• Stem cell differentiation
• Myeloid lineage
• Lymphoid lineage
• Cytokines
• Growth factors
• Erythropoietin
• Thrombopoietin
• Colony-stimulating factors

💡 Important:
Cadherins → mainly cell-cell adhesion
Integrins → cell-ECM adhesion and signaling
Selectins → cell recognition and leukocyte adhesion
Connexins → gap junction formation

C. Innate and Adaptive Immune System

🛡️ 1. Innate Immunity

• Physical barriers
• Skin and mucosal barriers
• Phagocytes
• Neutrophils
• Macrophages
• Dendritic cells
• Natural killer cells
• Complement system
• Inflammatory mediators

🧬 2. Adaptive Immunity

• B lymphocytes
• T lymphocytes
• Humoral immunity
• Cell-mediated immunity
• Antigen specificity
• Immunological memory

🧪 3. Antigens

• Antigen
• Antigenicity
• Immunogenicity
• Epitope
• Paratope
• Hapten
• Carrier molecules

🧬 4. B and T Cell Epitopes

• B-cell epitopes
• Linear epitopes
• Conformational epitopes
• T-cell epitopes
• MHC-dependent antigen recognition

🧬 5. Antibody Structure

• Immunoglobulin structure
• Heavy chains
• Light chains
• Variable regions
• Constant regions
• Fab region
• Fc region
• Disulfide bonds
• Antigen-binding site

🧪 6. Classes of Immunoglobulins

• IgG
• IgM
• IgA
• IgE
• IgD
• Structure and functions of each class

🔀 7. Generation of Antibody Diversity

• V(D)J recombination
• V, D and J gene segments
• RAG1 and RAG2
• Junctional diversity
• Combinatorial diversity
• Somatic hypermutation
• Class-switch recombination
• AID enzyme

🧪 8. Monoclonal Antibodies

• Hybridoma technology
• B-cell fusion
• Myeloma cells
• Selection of hybridomas
• Monoclonal antibody production
• Applications of monoclonal antibodies

🧬 9. Antibody Engineering

• Chimeric antibodies
• Humanized antibodies
• Fully human antibodies
• Fab fragments
• Single-chain variable fragments
• Therapeutic antibodies

🔗 10. Antigen-Antibody Interactions

• Affinity
• Avidity
• Specificity
• Cross-reactivity
• Precipitation
• Agglutination
• ELISA
• Western blot
• Immunofluorescence

🧬 11. MHC Molecules

• MHC class I
• MHC class II
• Antigen-binding cleft
• MHC polymorphism
• HLA molecules
• CD8 recognition of MHC I
• CD4 recognition of MHC II

📦 12. Antigen Processing and Presentation

• Endogenous antigen pathway
• MHC class I pathway
• Proteasome
• TAP transporter
• ER loading
• Exogenous antigen pathway
• MHC class II pathway
• Endosomal processing
• Invariant chain
• CLIP

🧬 13. B Cell Activation

• B-cell receptor
• Antigen recognition
• T-dependent activation
• T-independent activation
• Helper T-cell interaction
• Germinal center reaction
• Plasma cells
• Memory B cells

🧬 14. T Cell Activation

• T-cell receptor
• Antigen recognition
• MHC recognition
• Co-stimulation
• CD28
• B7 molecules
• T-cell receptor signaling
• T-cell differentiation

🛡️ 15. T Cell Subsets

• Helper T cells
• Th1
• Th2
• Th17
• T follicular helper cells
• Regulatory T cells
• Cytotoxic T cells

🧪 16. Humoral Immune Response

• Antibody production
• Plasma cell differentiation
• Memory B cells
• Primary immune response
• Secondary immune response
• Affinity maturation
• Class switching

🧬 17. Cell-Mediated Immunity

• Cytotoxic T lymphocytes
• Target cell killing
• Perforin
• Granzymes
• Fas-FasL pathway
• Macrophage activation

🧬 18. Complement System

• Classical pathway
• Lectin pathway
• Alternative pathway
• C3 activation
• C3 convertase
• C5 convertase
• Membrane attack complex
• Opsonization
• Inflammation

🧬 19. Toll-Like Receptors

• Pattern recognition receptors
• Pathogen-associated molecular patterns
• TLR signaling
• NF-κB activation
• Inflammatory cytokines
• Innate immune recognition

🔥 20. Inflammation

• Acute inflammation
• Chronic inflammation
• Histamine
• Prostaglandins
• Cytokines
• Leukocyte recruitment
• Vascular permeability
• Inflammatory signaling

⚠️ 21. Hypersensitivity

• Type I hypersensitivity
• Type II hypersensitivity
• Type III hypersensitivity
• Type IV hypersensitivity
• Immediate hypersensitivity
• Delayed-type hypersensitivity

🧬 22. Autoimmunity

• Self-tolerance
• Breakdown of self-tolerance
• Autoantibodies
• Autoimmune diseases
• Central tolerance
• Peripheral tolerance

🦠 23. Immune Responses to Pathogens

• Immune response to bacterial infections
• Immune response to viral infections
• Immune response to parasitic infections
• Innate immune defense
• Adaptive immune defense

⚠️ 24. Immunodeficiencies

• Primary immunodeficiency
• Secondary immunodeficiency
• Congenital immunodeficiency
• Acquired immunodeficiency
• HIV/AIDS
• Immune system defects

💉 25. Vaccines

• Live attenuated vaccines
• Inactivated vaccines
• Subunit vaccines
• Toxoid vaccines
• Conjugate vaccines
• Viral vector vaccines
• Nucleic acid vaccines
• mRNA vaccines
• Primary and booster responses

🧠 Immunology Core Concept:
Antigen → APC → MHC → T-cell receptor → T-cell activation → Cytokines / effector functions → Immune response

MHC I → CD8⁺ T cells → Cytotoxic response
MHC II → CD4⁺ T cells → Helper response

D. Host–Pathogen Interaction

🦠 1. Pathogen Recognition

• Host-pathogen recognition
• Pattern recognition receptors
• Pathogen-associated molecular patterns
• Innate immune recognition
• Adhesion molecules

🦠 2. Bacterial Entry into Host Cells

• Adhesion to host cells
• Invasion
• Phagocytosis manipulation
• Intracellular survival
• Type III secretion systems
• Type IV secretion systems

🦠 3. Viral Entry

• Viral attachment
• Host-cell receptors
• Membrane fusion
• Endocytosis
• Viral penetration
• Uncoating

🧬 4. Pathogen-Mediated Alteration of Host Cells

• Alteration of signaling pathways
• Manipulation of host transcription
• Manipulation of host translation
• Inhibition of apoptosis
• Immune evasion
• Alteration of cytoskeleton
• Manipulation of intracellular trafficking

🦠 5. Pathogen Virulence

• Virulence factors
• Toxins
• Adhesins
• Invasins
• Capsules
• Secretion systems
• Biofilms

🧬 6. Virus-Induced Cell Transformation

• Viral oncogenes
• Cellular transformation
• Altered cell cycle
• Inhibition of apoptosis
• Uncontrolled proliferation
• Virus-associated cancers

🌱 7. Pathogen-Induced Diseases in Plants

• Plant-pathogen recognition
• Pattern-triggered immunity
• Effector-triggered immunity
• Plant defense signaling
• Hypersensitive response
• Systemic acquired resistance

🧬 8. Cell-Cell Fusion

• Normal physiological cell fusion
• Fertilization
• Myoblast fusion
• Immune cell fusion
• Pathological cell fusion
• Viral-mediated cell fusion
• Syncytium formation

🎯 CSIR-NET Focus:
Host receptor recognition, bacterial invasion, viral entry, secretion systems, virulence factors, immune evasion and virus-induced transformation are major areas of this section.

E. Cancer

🧬 1. Cancer Biology

• Definition of cancer
• Benign and malignant tumors
• Hallmarks of cancer
• Uncontrolled cell proliferation
• Loss of growth control
• Resistance to cell death

🧬 2. Genetic Rearrangements

• Chromosomal translocations
• Gene amplification
• Gene deletion
• Inversions
• Chromosomal instability
• Fusion genes

🔴 3. Oncogenes

• Proto-oncogenes
• Oncogenes
• Gain-of-function mutations
• Growth factors
• Growth factor receptors
• Signal transduction proteins
• Transcription factors
• RAS
• MYC

🛡️ 4. Tumor Suppressor Genes

• Definition
• Loss-of-function mutations
• p53
• RB
• BRCA genes
• Cell cycle checkpoint control
• DNA damage response

🔄 5. Cancer and Cell Cycle

• Cell cycle checkpoints
• Cyclins
• CDKs
• CDK inhibitors
• p53 pathway
• Rb pathway
• Loss of cell cycle control

🦠 6. Virus-Induced Cancer

• Oncogenic viruses
• Viral oncogenes
• HPV
• EBV
• Hepatitis B virus
• Hepatitis C virus
• HTLV-1
• Viral transformation

🧬 7. Metastasis

• Local invasion
• Basement membrane degradation
• Extracellular matrix remodeling
• Intravasation
• Circulation of tumor cells
• Extravasation
• Secondary tumor formation

🔗 8. Cancer Cell Interaction with Normal Cells

• Tumor microenvironment
• Stromal cells
• Fibroblasts
• Immune cells
• Angiogenesis
• Extracellular matrix
• Cell adhesion
• Cell signaling

🩸 9. Angiogenesis

• Tumor-induced blood vessel formation
• VEGF
• Endothelial cell proliferation
• Vascular remodeling
• Role of angiogenesis in tumor growth

💊 10. Therapeutic Interventions

• Chemotherapy
• Radiotherapy
• Targeted therapy
• Monoclonal antibody therapy
• Kinase inhibitors
• Hormonal therapy
• Immunotherapy
• Immune checkpoint inhibitors
• CAR-T cell therapy
• Anti-angiogenic therapy

🎯 Cancer Core Concept:

• Oncogene activation → Gain of function
• Tumor suppressor loss → Loss of growth control
• DNA repair defects → Genomic instability
• Cell-cycle deregulation → Uncontrolled proliferation
• Metastasis → Spread to distant tissues

🎯 CSIR-NET High-Yield:
Oncogenes vs tumor suppressor genes, p53, Rb, cell-cycle checkpoints, cancer-causing viruses, metastasis, angiogenesis and targeted cancer therapy are especially important.

📚 CSIR-NET Unit 4 – Quick Revision Map

A → Cell Signaling

B → Cellular Communication

C → Innate & Adaptive Immunity

D → Host–Pathogen Interaction

E → Cancer Biology

🎯 Most Important CSIR-NET Topics

• GPCR signaling and G-proteins
• cAMP, IP₃, DAG and Ca²⁺ signaling
• RTK and MAPK pathway
• PI3K-Akt pathway
• JAK-STAT signaling
• Two-component signaling systems
• Plant light signaling
• Bacterial chemotaxis
• Quorum sensing
• Cell adhesion molecules
• Gap junctions
• Extracellular matrix and integrins
• Neurotransmission
• Innate vs adaptive immunity
• Antibody structure and immunoglobulin classes
• V(D)J recombination and antibody diversity
• Monoclonal antibody production
• MHC I vs MHC II
• Antigen processing and presentation
• B-cell and T-cell activation
• Complement pathways
• Toll-like receptors
• Hypersensitivity and autoimmunity
• Vaccines and immunological memory
• Host-pathogen recognition and invasion
• Viral entry and immune evasion
• Oncogenes and tumor suppressor genes
• p53 and Rb pathways
• Virus-induced cancer
• Metastasis and angiogenesis
• Cancer immunotherapy

📖 Recommended Study Sequence:

📡 Cell Signaling → 🔗 Cellular Communication → 🛡️ Innate Immunity → 🧬 Adaptive Immunity → 🦠 Host–Pathogen Interaction → 🎗️ Cancer Biology