《分子细胞生物学》 Chapter 6 Cytoplasmic matrix, Endomembrane system, Protein Sorting and membrane trafficking

Chapter 6 Cytoplasmic matrix, Endomembrane system, Protein Sorting and membrane trafficking Learning objective 1. Compartmentalization in Eukaryotic Cells 2. The structural and functional relationship among the er, Golgi complexes, lysosomes and plasma membranes of eukaryotic cells: 3. The pathways of proteins targeting and sorting, and its mechanisms, 4. The ways of protein modifications and intracellular sites after they are synthesized; 5. Types of vesicle transport and their functions

Chapter 6 Cytoplasmic matrix, Endomembrane system, Protein Sorting and membrane trafficking Learning objective 1. Compartmentalization in Eukaryotic Cells; 2. The structural and functional relationship among the ER, Golgi complexes, lysosomes and plasma membranes of eukaryotic cells; 3. The pathways of proteins targeting and sorting, and its mechanisms; 4. The ways of protein modifications and intracellular sites after they are synthesized; 5. Types of vesicle transport and their functions

1. The Compartmentalization in Eukaryotic Cells Membranes divide the cytoplasm of eukaryotic cells into distinct compartments Three categories in eukaryotic cells: 1)the endomembrane system: ER, Golgi complex, Lys secretory vesicles (2)the cytoso ()mitochondria, chloroplasts, peroxisomes, and the nucleus Membrane-bound structures(organelles) are found in all eukaryotic cells

1. The Compartmentalization in Eukaryotic Cells ❖Membranes divide the cytoplasm of eukaryotic cells into distinct compartments. Three categories in eukaryotic cells: (1) the endomembrane system: ER, Golgi complex, Lys., secretory vesicles. (2) the cytosol. (3) mitochondria, chloroplasts, peroxisomes, and the nucleus. ❖Membrane-bound structures (organelles) are found in all eukaryotic cells

A Cytoplasmic matrix(Cytosol) and Endomembrane system &Cytoplasmic matrix and its functions >Cytoplasmic Matrix: The region of fluid content of the cytoplasm outside of the membranous organelles. Aqueous solution of large and small molecules including filaments of cytoskeleton which act as organizer for some order. The cytosol is the site of protein synthesis and degradation or modification. It also performs most of the cell,s intermediary metabolism

❖Cytoplasmic matrix and its functions ➢Cytoplasmic Matrix: The region of fluid content of the cytoplasm outside of the membranous organelles. Aqueous solution of large and small molecules including filaments of cytoskeleton which act as organizer for some order. ➢The Cytosol is the site of protein synthesis and degradation or modification. It also performs most of the cell’s intermediary metabolism. A. Cytoplasmic matrix (Cytosol) and Endomembrane System

Functions of cytoplasmic matrix: The protein synthesis, degradation and modification. 8 hsp70 discard by hsp70 machiner hsp60-like hsp60-like machinery machinery ribosome correctly folded protein correctly folded protein Cells carefully monitor the amount of misfolded proteins. An accumulation of misfolded proteins in the cytosol triggers a heat shock response, which stimulates the transcription of genes encoding cytosolic chaperones that help to refold the proteins

Functions of cytoplasmic matrix: The protein synthesis, degradation and modification. Cells carefully monitor the amount of misfolded proteins. An accumulation of misfolded proteins in the cytosol triggers a heat￾shock response, which stimulates the transcription of genes encoding cytosolic chaperones that help to refold the proteins

(1 MISFOLDED PROTEINS IN ER SIGNAL nuclear NUCLEUS THE NEED FOR MORE ER CHAPERONES envelope BY ACTIVATING A TRANSMEMBRANE chaperone mRNA KINASE 2 ACTIVATED KINASE TURNS INTO AN ENDORIBONUCLEASE CYTOSOL gene regulatory (3 ENDORIBONUCLEASE CUTS SPECIFIC protein RNA MOLECULES AT TWO POSITIONS REMOVING AN INTRON ER chaperone 8曾 4 TWO EXONS ARE LIGATED TO mRNA D exon exon FORM AN ACTIVE mRNA 5 mRNA IS TRANSLATED TO MAKE A GENE REGULATORY PROTEIN pre-mRNA transmembrane 6 GENE REGULATORY PROTEIN ENTERS protein kinase (sensor intron NUCLEUS AND ACTIVATES GENES ENCODING ER CHAPERONES ribonuclease domain 7 CHAPERONES ARE MADE IN ER WHERE THEY HELP FOLD PROTEINS misfolded protein ER LUMEN Figure 12-56 The unfolded protein response in yeast. By this intracellular signaling pathway, the accumulation of misfolded proteins the ER lumen signals to the nucleus to activate the transcription of that encode proteins that help the cell to cope with the abundance of misfolded proteins in the ER

B Endomembrane system Plasma membrane Extracellular medium Endocytic Lysosome Perinuclear space Transport vesicles endosome Late complex vesicles Smooth endoplasmic Ribosomes reticulum endoplasmic reticulum Peroxisomes Cytosol Endomembrane System The structural and functional relationship organelles including ER, Golgi complex, lysosome, endosomes, secretory vesicles. .Membrane-bound structures(organelles) are found in all eukaryotic cells

B. Endomembrane System ❖Endomembrane System : The structural and functional relationship organelles including ER,Golgi complex, lysosome, endosomes, secretory vesicles. ❖Membrane-bound structures (organelles) are found in all eukaryotic cells

Relative volumes occupied by the major intracellular compartments in Liver Cell Intracellular compartment of total cell volume Cytosol 54 Mitochondria Rough er cisternae Smooth er cisternae plus golgi cisternae N ucleus 6 Peroxisome lysosomes Endosomes

Intracellular compartment % of total cell volume Cytosol 54 Mittchondria 22 Rough ER cisternae 9 Smooth ER cisternae plus Golgi cisternae 6 Nucleus 6 Peroxisome 1 Lysosomes 1 Endosomes 1 Relative volumes occupied by the major intracellular compartments in Liver Cell

C. The dynamic Nature of the Endomembrane system o Most organelles are part of a dynamic system in which vesicles move between compartments Biosynthetic pathways move proteins, carbohydrates and lipids within the cell Secretory pathways discharge proteins from cells Endocytic pathways move materials into cells Sorting signals are recognized by receptors and target proteins to specific sites

C. The Dynamic Nature of the Endomembrane System ❖Most organelles are part of a dynamic system in which vesicles move between compartments. ❖Biosynthetic parthways move proteins, carbohydrates and lipids within the cell. ❖Secretory pathways discharge proteins from cells. ❖Endocytic parthways move materials into cells. ❖Sorting signals are recognized by receptors and target proteins to specific sites

D. A few approaches to the study of cytomembranes Insights gained from autoradiography; Insights gained from the biochemical analysis of subcellular fractions o Insights gained from the study of genetic mutants The dynamic activities of endomembrane systems are highly conserved despite the structural diversity of different cell types

D. A few approaches to the study of cytomembranes ❖ Insights gained from autoradiography; ❖ Insights gained from the biochemical analysis of subcellular fractions; ❖Insights gained from the study of genetic mutants; The dynamic activities of endomembrane systems are highly conserved despite the structural diversity of different cell types

De duve. A Claude and G Palade. 1974 Nobel prize olg vesicle Tume of chase (min) Lumen Gcln complex Mitochondna 20 min

De Duve, A.Claude and G.Palade,1974 Nobel Plrize