Related Experiment Videos
An abnormal calcium uptake pump in Chediak-Higashi neutrophil lysosomes
B Styrt1, C R Pollack, M S Klempner
1Department of Medicine, Michigan State University, East Lansing 48824.
Insights
Lysosomes in Chediak-Higashi syndrome (CHS) exhibit increased calcium uptake, suggesting altered calcium transport pumps contribute to cellular defects in this genetic disorder.
Area of Science:
- Cell Biology
- Immunology
- Genetics
Background:
- Calcium mobilization is crucial for phagocyte activation and stimulus-response coupling.
- Lysosomes sequester calcium within neutrophils.
- Chediak-Higashi syndrome (CHS) is characterized by abnormal lysosome morphology and impaired neutrophil function.
Purpose of the Study:
- To investigate ATP-dependent calcium uptake in neutrophil lysosomes from beige mice, a model for CHS.
- To determine if altered calcium transport is associated with CHS-related cellular defects.
Main Methods:
- Isolation of neutrophil lysosomes from beige mice (CHS model) and control mice.
- Measurement of ATP-dependent calcium uptake kinetics in isolated lysosomes.
- Analysis of kinetic parameters including Vmax and Km for ATP and calcium.
Main Results:
- Lysosomes from CHS mice demonstrated an enhanced capacity for ATP-dependent calcium uptake compared to controls.
- Kinetic analysis revealed significant differences in Vmax and Km for both ATP and calcium.
- These findings suggest alterations in both the quantity and substrate affinity of lysosomal calcium uptake pumps in CHS.
Conclusions:
- A genetically determined abnormality in a subcellular calcium transport system likely contributes to the structural and functional defects observed in CHS cells.
- Altered lysosomal calcium handling may be a key factor in the pathophysiology of Chediak-Higashi syndrome.
Abstract:
Calcium is mobilized from intracellular stores during phagocyte activation and appears to be involved in stimulus-response coupling in these and other cell types. Because the lysosome is a calcium-sequestering organelle in the neutrophil and abnormal lysosome morphology is associated with defective neutrophil function in Chediak-Higashi syndrome (CHS), we examined ATP-dependent calcium uptake in neutrophil lysosomes from the beige mouse model of CHS. We present findings indicating that CHS lysosomes have an enhanced capacity for ATP-dependent calcium uptake relative to control lysosomes. Kinetic analysis showed differences in Vmax and in the Km for both ATP and calcium, suggesting that both the number of lysosomal calcium uptake pumps and their substrate affinity may be altered in CHS. We conclude that a genetically determined abnormality of a subcellular calcium transport system may contribute to the structural and functional defects of CHS cells.