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Extramitochondrial localization of mortalin/mthsp70/PBP74/GRP75

Q Ran1, R Wadhwa, R Kawai

  • 1Roy M. and Phyllis Gough Huffington Center on Aging, Department of Pathology, Baylor College of Medicine, One Baylor Plaza, Houston, Texas, 77030, USA.

Biochemical and Biophysical Research Communications
|August 17, 2000
PubMed

Insights

Mortalin, a heat shock protein 70 (HSP70) family member, is found in mitochondria and endoplasmic reticulum (ER) in human cell lines. Some cell lines also show cytosolic mortalin, indicating varied intracellular localization.

Area of Science:

  • Cell biology
  • Molecular biology
  • Protein localization

Background:

  • Mortalin, a mitochondrial homologue of the heat shock protein 70 (HSP70) family, is crucial for cell function.
  • Previous studies suggested mortalin's primary localization to mitochondria.

Purpose of the Study:

  • To investigate the precise intracellular localization of mortalin in immortal human cell lines.
  • To determine if mortalin's distribution varies across different cell lines.

Main Methods:

  • Subcellular fractionation techniques were employed.
  • Immunofluorescence microscopy was utilized to visualize mortalin's location.
  • Analysis was performed on human cell lines from complementation groups A-D.

Main Results:

  • Mortalin was identified in both mitochondria and endoplasmic reticulum (ER) fractions across all analyzed cell lines.
  • A cytosolic pool of mortalin was observed in specific Group A cell lines (EJ, GM639, HT1080).
  • These findings reveal that mortalin is not exclusively mitochondrial.

Conclusions:

  • Mortalin exhibits differential intracellular localization, residing in mitochondria, ER, and cytoplasm.
  • The varied organelle residence of mortalin may explain previously observed distribution differences in human cell lines.

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