Lectures in University of Brawijaya, 2013

Biological Responses to Environmental Stress

Tetsuro Ishii, PhD.

Professor Emeritus, University of Tsukuba, Japan

Animal

Plant

poisons

Detoxification systemNatural immunityRepair systemApoptosis

Animals have developed defense system against environmental stress agents

Toxic agents

UV, As, Heavy metals

Infection

Bacteria, Virus

Stress causes upregulation of stress proteins

stressor Detection by sensors

Gene activation

Protein synthesisRepair damages

Cell damages

Acquire tolerance

Activation of transcription factors

Heat shockOxidative stress

HSFsNrf2

Biological Responses to Environmental Stress

1. Cellular response to heat

2. Cellular response to electrophiles and reactive oxygen species

3. Nrf2 target genes

Heat was necessary to create life

Adaptation to heat is most important for life.

Yellowstone hot spring

Hydrothermal vent

Heat shock induces various proteins in cells

37°C 43°C

Temperature shift

Induction of heat shock proteins (HSPs)Has60, Hsp70, Hsp90, etc.

Activation of heat shock factors

Heat shock protein (HSP) family

HSP110HSP100HSP90HSP70 (DNAK)HSP60 (chaperonin, GroEL)HSP47HSP40 (DNAJ)HSP33HSP27HSP15HSP10

Some of these proteins are constitutively expressed and play their roles under normal temperature.

Some proteins return to native form following heat denaturation

denature or unfolding

Renature or refolding

But, many proteins became aggregated when denatured

Denatured/unfolded proteins tend to aggregate

Protein aggregates

Inhibition of protein aggregation by Dank-ClpB

Heat shock

Aggregation

Native form

Chaperonin inhibits protein aggregation

Native form

Denatured form

Urea + DTT

± chaperonin

albumin

Enzyme activity

turbidity

Opitical Scattering

Inhibition of protein aggregate by chaperonin

ATP-dependent folding of GFP-protein by chaperonin

GFP fluorescence

(+) chaperonin

(-) chaperonin

Time (min)

Time (min)

Without chaperonin

With chaperonin

Chaperonin inhibits protein aggregate by heat treatment

Double ring structure of chaperonin, GroEL

GroEL-GroES complex provides space for protein folding

Discovery of chaperonin

“Molecular chaperon” was found in different systems

Functions of chaperonin during protein synthesis

chaperonin

hsp

normal folding

aggregates

Protein synthesis

Miss-folding

Role of chaperons in protein synthesis

Role of chaperons in protein targeting to mitochondria