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Related Concept Videos

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Updated: May 16, 2025

Defining Hsp33's Redox-regulated Chaperone Activity and Mapping Conformational Changes on Hsp33 Using Hydrogen-deuterium Exchange Mass Spectrometry
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Hsp70 chaperones, Ssa1 and Ssa2, limit poly(A) binding protein aggregation.

Hannah E Buchholz1, Sean A Martin1, Jane E Dorweiler1

  • 1Department of Biological Sciences, Marquette University, Milwaukee, WI 53201-1881.

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Loss of Hsp70 chaperones in yeast causes endogenous Pab1 protein aggregation. Overexpressing other chaperones like Hsp104 and Sis1 can prevent this, suggesting Hsp70

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Area of Science:

  • Cellular Biology
  • Protein Homeostasis
  • Molecular Chaperones

Background:

  • Hsp70 chaperones are crucial for protein folding and preventing aggregation.
  • Yeast lacking Ssa1 and Ssa2 Hsp70s exhibit reduced growth and lifespan.
  • The behavior of endogenous proteins in Hsp70-deficient cells is not well understood.

Purpose of the Study:

  • To investigate the aggregation of endogenous wild-type Poly A binding protein (Pab1) in yeast with limited Hsp70.
  • To determine if other chaperones can compensate for Hsp70 deficiency.
  • To understand the role of Hsp70 in age-related protein aggregation.

Main Methods:

  • Utilized yeast strains deficient in Ssa1 and Ssa2 Hsp70 proteins.
  • Observed the formation of large Pab1 inclusions under normal and heat shock conditions.
  • Assessed the effect of overexpressing Ssa1, Hsp104, and Sis1 on Pab1 aggregation.
  • Analyzed stress granule dynamics in the presence of Pab1 inclusions.

Main Results:

  • Wild-type Pab1 forms large cytoplasmic inclusions in approximately half of ssa1Δssa2Δ yeast cells without stress.
  • Overexpression of Ssa1, Hsp104, or Sis1 significantly reduces Pab1 inclusion formation.
  • Stress granules form independently of Pab1 inclusions, but co-occurrence slows disassembly.
  • Pab1 inclusions also form in saturated wild-type cultures and can be partially rescued by Ssa1 overexpression.

Conclusions:

  • Hsp70 chaperones limit endogenous protein aggregation in healthy cells.
  • Depletion of active Hsp70 may drive age-related protein aggregation.
  • Other chaperones like Hsp104 and Sis1 can partially compensate for Hsp70 loss.