Differential subcellular distribution of mortalin in mortal and immortal mouse and human fibroblasts
1National Institute of Bioscience and Human-Technology, Agency of Industrial Science and Technology, Ibaraki, Japan.
Abstract:
Mortalin, p66mot-1, from the cytosolic fractions of mouse embryonic fibroblasts (MEF) has been identified. We have cloned and characterized it as a novel member of mouse hsp70 family [R. Wadhwa, S. C. Kaul, Y. Ikawa, and Y. Sugimoto (1993) J. Biol. Chem. 268, 6615-6621]. We report that immortal clones from MEF such as NIH 3T3, RS4, and Balb/c 3T3 harbor the same or a very similar protein but in the perinuclear locale. Biochemical analysis revealed that the proteins from mortal (MEF) and immortal (NIH 3T3) fibroblasts do not show gross differences. However, the phenomenon of differential distribution of p66 protein in mortal and immortal fibroblasts is conserved in three different strains of mouse and, interestingly, in human fibroblasts, too. The data suggest that at least one common step is involved in immortalization of mouse and human fibroblasts and also point to the practical implication(s) of such easily detectable differences.
Insights
Mortalin (p66mot-1) protein differs in location between mortal and immortal mouse and human fibroblasts. This differential distribution suggests a common step in fibroblast immortalization.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Mortalin, also known as p66mot-1, is a novel member of the mouse hsp70 family.
- This protein was initially identified in the cytosolic fractions of mouse embryonic fibroblasts (MEF).
Purpose of the Study:
- To investigate the localization of mortalin (p66mot-1) in both mortal and immortal fibroblasts.
- To determine if the differential distribution of mortalin is conserved across different mouse strains and in human fibroblasts.
- To explore potential implications of mortalin's localization in fibroblast immortalization.
Main Methods:
- Cloning and characterization of mortalin (p66mot-1).
- Biochemical analysis of mortalin in mortal (MEF) and immortal (NIH 3T3) fibroblasts.
- Comparative analysis of mortalin distribution in various mouse fibroblast strains and human fibroblasts.
Main Results:
- Immortal MEF clones (NIH 3T3, RS4, Balb/c 3T3) harbor mortalin (p66mot-1) in the perinuclear locale, unlike mortal MEF.
- Biochemical analysis showed no gross differences in the mortalin protein between mortal and immortal fibroblasts.
- Differential distribution of p66 protein was conserved across three mouse strains and in human fibroblasts.
Conclusions:
- The perinuclear localization of mortalin (p66mot-1) in immortal fibroblasts distinguishes them from mortal counterparts.
- The conserved differential distribution suggests a common mechanism in the immortalization of mouse and human fibroblasts.
- This easily detectable difference in mortalin localization may have practical implications for studying immortalization.
