Heat Shock Protein (stress protein)

STRESS PROTEINS:

When cells are exposed to stress, protective response of the cell brings into play a group of proteins called stress proteins.

These proteins are released from the endoplasmic reticulum, and they move molecules within a cell.

Two types:

1.HSP (HEAT SHOCK PROTEINS)

2. Ubiquitins

HEAT SHOCK PROTEINS:
Intra cellular carrier proteins.

Present in most cells especially in renal tubular epithelial cells.

Normally perform the function of molecular chaperones (hsp90) (proteins that are involved in house keeping).

Example: 1. Protein misfolding

2. Disaggregation of proteins and protein complexes

3. Transport of proteins into various intracellular organelles (protein kinesis)

Stress (toxins, drugs, poison, ischemia) —-> increased levels of stress proteins within a cell —-> leakage of stress proteins into the plasma.
This plays a role in myocardial infarction, amyloidosis etc.
They are often classified based on their molecular weight: hsp10, hsp40, hsp60, hsp70, hsp90
The term “heat shock protein” is a misnomer because many agents other than heat induce the expression of the heat shock protein gene.

Two main functions:

When new protein molecules are being produced by ribosome within the cell: HSP aids in correct folding of polypeptide chain into functional protein. Assures that the new protein will assume its functional three-dimensional configuration.
Stress event --> heat shock proteins also assist in refolding or degradation of damaged or denatured proteins.

UBIQUITIN:

Directs intracellular molecules for degradation or for synthesis.

Role in

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