덕성여자대학교 약학과

조효선 교수

Fig. 4.5. Rearrangement of V, D, J gene segments guided by RSSs RSSs : recombination signal sequences 재조합 신호서열 Heptamer(conserved)--spacer(12 or 23 bp ; nonconserved)--nonamer(conserved) 12/23 rules; gene segment with 12bp spacer only join to 23bp spacer e.g., in heavy chain rearragement, VH can not join JH gene segment directly

Chapter 8;항원수용체 (Antigen receptor)

Chapter 8;항원수용체 (Antigen

receptor)

Fig. 4.7. Enzymatic steps in RAG-dependent V(D)J rearrangement RAG1,2 ; V(D)J recombinase, cut RSSs, create hairpin

Ku70:Ku80 ; bind to hairpin

DNA-PK, DNA dependent protein kinase, Artemis ; open the hairpin (cut at random site)

TdT, terminal deoxynucleotidyl transferase ; add nucleotides randomly

DNA ligase; ligate DNA ends

- Rearrangement of V, (D), J gene segments = V(D) J recombination Defect(mutation) in RAG ; SCID(severe combined immune deficiency) in mice Omenn syndrome in human - Combinatorial diversity : multiple different copies of each type of gene segment different combinations of gene segments many possible different combinations of H and L chain V regions e.g., V1-D2-J1, V2-D1-J6 - Junctional diversity ; addition or subtraction of nucleotides at the joints by recombination process e.g., N-nucleotides

Chapter 8;항원수용체 (Antigen receptor)

Fig.4.18. Coexpression of IgD and IgM is regulated by RNA processing

- IgD & IgM coexpressed on the surface of mature B cells - primary mRNA transcript that differentially spliced to distinct mRNA molecule e.g., VDJ exon linked to Cμ exon to encode μ heavy chain

Chapter 8;항원수용체 (Antigen receptor)

성숙 B 세포

IgD

IgM

미성숙 B 세포

IgM

골수 림프절 Ag

Fig. 4.21. Secondary diversification of the antibody (항체의 2차 다양성)

- occurs in activated B cells - driven by antigen 1. Somatic hypermutation (체세포 과돌연변이) ; mutations introduced to heavy c

hain or light chain V regions, altering the affinity of the antibody for its antigen

2. Gene conversion ;rearranged V region is modified

by the introduction of sequences derived from V gene segment

3. Class switching(클래스 전환) ;initial μ heavy chain C regions ar

e replaced another isotype, modifying effector activity, not antigen specificity

Chapter 8;항원수용체 (Antigen receptor)

B cell signaling

Chapter 6. Signaling through immune system receptors (From Janeway’s immunobiology, 7ed)

By Cell signaling technology

1

2?

3 ?

4

B(T) 세포

Ag

Chapter 6. Signaling through immune system receptors

General principles of signal transduction

1) Extracellular signal

2) Transmembrane receptor

3) Intracellular signaling pathway (signal transduction)

4) Alteration of gene expression

1

2?

3 ?

4

B(T) 세포

Ag

Fig. 6.1. two types of receptors that signal through protein kinases - Phosphorylation occurs in tyrosine, serine, threonine

- two types of receptors for kinase activity : part of receptor or associate with receptor

Chapter 6. Signaling through immune system receptors

Fig. 6.3 Assembly of signaling complexes is mediated by scaffold and adaptor proteins

- Scaffold proteins (larger) : no enzyme activity, recruits many proteins - Adaptor proteins (smaller) : link two proteins together

SH2, SH3 : Src Homology domain

Fig. 6.6. Recruitment of signaling proteins

PIP2

PI 3-kinase PIP3

AKT, ITK binds to PIP3

PI 3-kinase : phosphatidylinositol 3-kinase PIP2 : phosphatidylinositol 4,5-biphosphate PIP3 : phosphatidylinositol 3,4,5-trisphosphate

p + p + p + sugar(당) + guanine(nucleic acid) GTP

p + p + sugar(당) + guanine(nucleic acid) GDP

GTPase

From WIKIPEDIA

From WIKIPEDIA

GEFs : guanine nucleotide exchange factors GAPs : GTPase-activating proteins e.g., Ras family (Ras, Rac, Rho, Cdc42) cell proliferation

Fig. 6.5. small G proteins = GTP-binding proteins = small GTPases

GDP-Gproteins

(inactive) GTP GAPs GEFs GDP

GTP-Gproteins (active)

PIP3 PIP2

From WIKIPEDIA From WIKIPEDIA

PI 3-kinase

Fig. 6.7. membrane lipid rafts

Small Sphingolipid + Cholesterol rich membrane rigidity 25~50% of plasma membrane dynamic structures most signaling occurs receptors move into lipid rafts GPI : glycosylphosphatidylinositol

Fig. 6.8. Terminating signaling = Dephosphorylation, Protein degradation

SHP : protein phosphatase Cbl : ubiqutin ligase