Background and Purpose-Diffusion-weighted imaging (DWI) may be a useful tool to evaluate the efficacy of cerebral protection devices in preventing thromboembolic complications during carotid angioplasty and stenting (CAS). The goals of this study were (1) to compare the frequency, number, and size of new DWI lesions after unprotected and protected CAS; and (2) to determine the clinical significance of these lesions. Methods-DWI was performed immediately before and within 48 hours after unprotected or protected CAS. Clinical outcome measures were stroke and death within 30 days. Results-The proportion of patients with any new ipsilateral DWI lesion (49% versus 67%; PϽ0.05) as well as the number of new ipsilateral DWI lesions (medianϭ0; interquartile range [IQR]ϭ0 to 3 versus medianϭ1; IQRϭ0 to 4; PϽ0.05) were significantly lower after protected (nϭ139) than unprotected (nϭ67) CAS. The great majority of these lesions were asymptomatic and less than 10 mm in diameter. Although there were no significant differences in clinical outcome between patients treated and not treated with protection devices (7.5% versus 4.3%, not significant), the number of new DWI lesions was significantly higher in patients who developed a stroke (medianϭ7.5; IQRϭ1.5 to 17) than in patients who did not (medianϭ0; IQRϭ1 to 3.25; PϽ0.01). Conclusions-The use of cerebral protection devices significantly reduces the incidence of new DWI lesions after CAS of which the majority are asymptomatic and less than 10 mm in diameter. The frequent occurrence of these lesions and their close correlation with the clinical outcome indicates that DWI could become a sensitive surrogate end point in future randomized trials of unprotected versus protected CAS.

The human peroxins PEX3 and PEX19 play a central role in peroxisomal membrane biogenesis. The membrane-anchored PEX3 serves as the receptor for cytosolic PEX19, which in turn recognizes newly synthesized peroxisomal membrane proteins. After delivering these proteins to the peroxisomal membrane, PEX19 is recycled to the cytosol. The molecular mechanisms underlying these processes are not well understood. Here, we report the crystal structure of the cytosolic domain of PEX3 in complex with a PEX19-derived peptide. PEX3 adopts a novel fold that is best described as a large helical bundle. A hydrophobic groove at the membranedistal end of PEX3 engages the PEX19 peptide with nanomolar affinity. Mutagenesis experiments identify phenylalanine 29 in PEX19 as critical for this interaction. Because key PEX3 residues involved in complex formation are highly conserved across species, the observed binding mechanism is of general biological relevance.Peroxisomes are single membrane-bound organelles that carry out a variety of metabolic processes. In addition to the degradation of H 2 O 2 , the ␤-oxidation of very long chain or branched chain fatty acids and the synthesis of ether lipids are performed in these subcellular compartments (1, 2). The biogenesis of peroxisomes, including their formation and proliferation, as well as the degradation of peroxisomes are highly dynamic processes that are adapted to metabolic needs (3). Defects in peroxisome biogenesis cause a number of severe inherited diseases, which are collectively referred to as peroxisome biogenesis disorders (4, 5). Studies in yeast and analysis of patients affected by these disorders have led to the identification of specific proteins involved in peroxisomal formation and maintenance (6). Fifteen such proteins, which are named peroxins, are currently known in humans and the corresponding genes (PEX genes) are highly conserved throughout the eukaryotic kingdom (7,8).All matrix proteins and most membrane proteins are imported post-translationally into peroxisomes. The machinery of peroxins that mediates the import of matrix proteins bearing a peroxisomal targeting signal is far better understood than the machinery that mediates the recognition and import of membrane proteins (9, 10). The peroxins PEX3, 5 PEX16, and PEX19 are known to be essential for peroxisomal membrane biogenesis as a loss of any of these proteins leads to the complete absence of detectable peroxisomal membrane structures (11). However, de novo formation of peroxisomes was observed in cells deficient for each of these peroxins upon complementation with the wild type gene, raising an intriguing question about the origin of the peroxisomal membrane (11-15). The endoplasmic reticulum membrane as the obvious source was disputed for a long time as several studies indicate that this process does not involve the classical coat protein I-and coat protein II-dependent pathways (16 -18). Recently, new evidence for an involvement of the endoplasmic reticulum as a peroxisomal precursor has been reported in ...

The human peroxins PEX3 and PEX19 are essential for peroxisome biogenesis. They mediate the import of membrane proteins as well as the de novo formation of peroxisomes. PEX19 binds newly synthesized peroxisomal membrane proteins post-translationally and directs them to peroxisomes by engaging PEX3, a protein anchored in the peroxisomal membrane. After protein insertion into the lipid bilayer, PEX19 is released back to the cytosol. Crystallographic analysis provided detailed insights into the PEX3-PEX19 interaction and identified three highly conserved regions, the PEX19-binding region, a hydrophobic groove and an acidic cluster, on the surface of PEX3. Here, we used site-directed mutagenesis and biochemical and functional assays to determine the role of these regions in PEX19-binding and peroxisome biogenesis. Mutations in the PEX19-binding region reduce the affinity for PEX19 and destabilize PEX3. Furthermore, we provide evidence for a crucial function of the PEX3-PEX19 complex during de novo formation of peroxisomes in peroxisome-deficient cells, pointing to a dual function of the PEX3-PEX19 interaction in peroxisome biogenesis. The maturation of preperoxisomes appears to require the hydrophobic groove near the base of PEX3, presumably by its involvement in peroxisomal membrane protein insertion, while the acidic cluster does not appear to be functionally relevant.Key words: affinity measurements, de novo peroxisome formation, membrane protein import, peroxin, peroxisomal membrane biogenesis, peroxisomal membrane protein, preperoxisome, protein-protein interaction