Demonstration of Three Distinct High-Molecular-Weight Complexes between Plasminogen Activator Inhibitor Type 1 and Tissue-Type Plasminogen Activator.

BACKGROUND: Details of the molecular interaction between tissue-type plasminogen activator (tPA) and plasminogen activator inhibitor type-1 (PAI-1) remain unknown. METHODS AND RESULTS: Three distinct forms of high-molecular-weight complexes are demonstrated. Two of the forms were detected by mass spectrometry. The high molecular mass detected by MALDI-TOF MS (matrix-assisted laser desorption ionization-time of flight mass spectrometry) was 107,029 Da, which corresponds to the sum of molecular masses of the intact tPA (65,320 Da) and the intact PAI-1 (42,416 Da). The lower molecular mass was 104,367 Da and is proposed to lack the C-terminal bait peptide of PAI-1 (calculated mass: 3,804 Da), which was detected as a 3,808 Da fragment. When the complex was analyzed by SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis), only a single band was observed. However, after treatment by SDS and Triton X-100, two distinct forms of the complex with different mobilities were shown by SDS-PAGE. The higher molecular weight band demonstrated specific tPA activity on fibrin autography, whereas the lower molecular weight band did not. Peptide sequence analysis of these two bands, however, unexpectedly revealed the existence of the C-terminal cleavage peptide in both bands and its amount was less in the upper band. In the upper band, the sequences corresponding to the regions at the interface between two molecules in its Michaelis intermediate were diminished. Thus, these two bands corresponded to distinct nonacyl-enzyme complexes, wherein only the upper band liberated free tPA under the conditions employed. CONCLUSION: These data suggest that under physiological conditions a fraction of the tPA-PAI-1 population exists as nonacylated-enzyme inhibitor complex.

Effect of subthalamic nucleus stimulation during exercise on the mesolimbocortical dopaminergic region in Parkinson's disease: a positron emission tomography study.

To elucidate the dynamic effects of deep brain stimulation (DBS) in the subthalamic nucleus (STN) during activity on the dopaminergic system, 12 PD patients who had STN-DBS operations at least 1 month prior, underwent two positron emission tomography scans during right-foot movement in DBS-off and DBS-on conditions. To quantify motor performance changes, the motion speed and mobility angle of the foot at the ankle were measured twice. Estimations of the binding potential of [(11)C]raclopride (BP(ND)) were based on the Logan plot method. Significant motor recovery was found in the DBS-on condition. The STN-DBS during exercise significantly reduced the [(11)C]raclopride BP(ND) in the caudate and the nucleus accumbens (NA), but not in the dorsal or ventral putamen. The magnitude of dopamine release in the NA correlated negatively with the magnitude of motor load, indicating that STN-DBS facilitated motor behavior more smoothly and at less expense to dopamine neurons in the region. The lack of dopamine release in the putamen and the significant dopamine release in the ventromedial striatum by STN-DBS during exercise indicated dopaminergic activation occurring in the motivational circuit during action, suggesting a compensatory functional activation of the motor loop from the nonmotor to the motor loop system.