Ischemia reperfusion-induced dynamic changes of protein tyrosine phosphorylation during human lung transplantation.
BACKGROUND
We have recently demonstrated that more than 20% of lung cells undergo apoptosis within the first 2 hr of graft reperfusion after human lung transplantation. It has been found that changes of protein tyrosine phosphorylation are involved in the regulation of apoptosis in various cell types.


METHODS
To determine the protein tyrosine phosphorylation status and related biochemistry changes, lung tissue biopsies were collected from six human lung transplant procedures after cold ischemic preservation (2-5 hr at 4 degrees C), after completing the implantation procedure (approximately 1 hr), and 1 or 2 hr after graft reperfusion. Western blotting was performed to determine protein tyrosine phosphorylation and several signal transduction proteins. Protein tyrosine kinase (PTK) and protein tyrosine phosphatase (PTP) activities were also measured.


RESULTS
Protein tyrosine phosphorylation was significantly increased after lung implantation and before reperfusion, and significantly decreased during the first 2 hr of graft reperfusion. The activity of Src PTKs was reduced by 50% during graft reperfusion, which was associated with a decrease of Src proteins and human actin filament associated protein, a cofactor for Src activation. PTP activity significantly decreased after lung implantation and remained at a low level 1 hr after reperfusion. After 2 hr of reperfusion, however, PTP activity returned to the basal level.


CONCLUSIONS
These dynamic changes of PTK and PTP likely explain the observed alterations of protein tyrosine phosphorylation. The significant decrease in protein tyrosine phosphorylation may be related to the observed apoptotic cell death during human lung transplantation.
Keshavjee
S
S
Thoracic Surgery Research Laboratory, University Health Network Toronto General Hospital, University of Toronto, Ontario, Canada.
Zhang
X M
XM
Fischer
S
S
Liu
M
M
D017209:Apoptosis / Q000502:physiology; D006801:Humans; D066298:In Vitro Techniques; D008168:Lung / Q000098:blood supply / Q000378:metabolism*; D055370:Lung Injury; D016040:Lung Transplantation / Q000009:adverse effects* / Q000473:pathology / Q000502:physiology*; D008840:Microfilament Proteins / Q000378:metabolism; D009926:Organ Preservation; D010766:Phosphorylation; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors; D011506:Proteins / Q000378:metabolism*; D015427:Reperfusion Injury / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D014443:Tyrosine / Q000378:metabolism; D019061:src-Family Kinases / Q000037:antagonists & inhibitors
D008840:Microfilament Proteins; D011506:Proteins; D014443:Tyrosine; D019061:src-Family Kinases; D017027:Protein Tyrosine Phosphatases