Related Experiment Videos
The influence of deletion mutations on phospholipase C-gamma 1 activity
D A Horstman1, A Chattopadhyay, G Carpenter
1Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee, 37232, USA.
Abstract:
Phospholipase C-gamma1, a substrate for many growth factor receptor and nonreceptor tyrosine kinases, produces second messenger molecules that are elements of signal transduction pathways related to cell proliferation. The influence of deletion mutations, which do not intrude on the domains required for catalytic function, on the basal activity of this enzyme is reported. Removal of the first 74 amino-terminal residues increases phospholipase C activity, while deletion of the carboxy-terminal 81 residues decreases enzyme activity. Deletion of the SH2-SH2-SH3 central region, which separates the two domains (X, Y) responsible for catalytic function, also increases enzymatic activity. Interestingly, addition of a recombinant SH2-SH2-SH3 fragment of phospholipase C-gamma1 to the holoenzyme inhibits its phospholipase activity at pH 7.0, but not at pH 5.0. However, addition of individual SH2 or SH3 domains does not influence activity of the holoenzyme. All three deletion mutants, in contrast to the holoenzyme, are relatively resistant to V8 proteolysis and activation induced by the epidermal growth factor receptor tyrosine kinase, which require, respectively, specific proteolysis and phosphorylation sites within the SH region. This suggests a conformational change is induced in the SH region by deletion at either the amino- or carboxy-terminus.
Insights
Altering phospholipase C-gamma1 (PLCγ1) enzyme structure impacts its activity and signaling. Deleting specific regions enhances basal activity and alters responses to growth factors, suggesting conformational changes.
Area of Science:
- Molecular Biology
- Enzymology
- Signal Transduction
Background:
- Phospholipase C-gamma1 (PLCγ1) is a key enzyme in cellular signaling pathways, producing second messengers crucial for cell proliferation.
- PLCγ1 is a substrate for tyrosine kinases, indicating its role in growth factor-mediated signaling cascades.
- Understanding the structure-function relationship of PLCγ1 is vital for deciphering its role in cell growth and disease.
Purpose of the Study:
- To investigate the impact of specific deletion mutations on the basal activity of Phospholipase C-gamma1 (PLCγ1).
- To determine how modifications in PLCγ1 structure affect its interaction with tyrosine kinases and its enzymatic properties.
- To explore the role of the SH2-SH2-SH3 domains in regulating PLCγ1 conformation and activity.
Main Methods:
- Construction and characterization of deletion mutants of PLCγ1, specifically targeting amino-terminal, carboxy-terminal, and central SH2-SH2-SH3 regions.
- Assay of basal phospholipase activity of wild-type and mutant PLCγ1 enzymes.
- Analysis of enzyme activity in response to recombinant SH2-SH2-SH3 fragments and V8 proteolysis.
- Investigation of activation by epidermal growth factor receptor tyrosine kinase.
Main Results:
- Deletion of the first 74 amino-terminal residues increased PLCγ1 activity, while deletion of the carboxy-terminal 81 residues decreased it.
- Removal of the central SH2-SH2-SH3 region also enhanced PLCγ1 enzymatic activity.
- Recombinant SH2-SH2-SH3 fragment inhibited PLCγ1 activity at pH 7.0 but not pH 5.0, suggesting pH-dependent conformational effects.
- Deletion mutants exhibited resistance to V8 proteolysis and epidermal growth factor receptor tyrosine kinase-induced activation, implying structural alterations in the SH region.
Conclusions:
- Specific deletions in PLCγ1, outside the catalytic domains, significantly modulate its basal enzymatic activity.
- The SH2-SH2-SH3 region plays a critical role in regulating PLCγ1 conformation and responsiveness to external stimuli like growth factors.
- Structural modifications in PLCγ1 can lead to altered signaling outputs, impacting cell proliferation pathways.