Citations

The mechanisms by which mammalian cells remodel the actin cytoskeleton in response to motogenic stimuli are complex and a topic of intense study. Dynamin 2 (Dyn2) is a large GTPase that interacts directly with several actin binding proteins, including cortactin. In this study, we demonstrate that Dyn2 and cortactin function to mediate dynamic remodeling of the actin cytoskeleton in response to stimulation with the motogenic growth factor platelet-derived growth factor. On stimulation, Dyn2 and cortactin coassemble into large, circular structures on the dorsal cell surface. These “waves” promote an active reorganization of actin filaments in the anterior cytoplasm and function to disassemble actin stress fibers. Importantly, inhibition of Dyn2 and cortactin function potently blocked the formation of waves and subsequent actin reorganization. These findings demonstrate that cortactin and Dyn2 function together in a supramolecular complex that assembles in response to growth factor stimulation and mediates the remodeling of actin to facilitate lamellipodial protrusion at the leading edge of migrating cells.

The degradation of extracellular matrix (ECM) by matrix metalloproteases is crucial in physiological and pathological cell invasion alike. Degradation occurs at specific sites where invasive cells make contact with the ECM via specialized plasma membrane protrusions termed invadopodia. Herein, we show that the dynamin 2 (Dyn2), a GTPase implicated in the control of actin-driven cytoskeletal remodeling events and membrane transport, is necessary for focalized matrix degradation at invadopodia. Dynamin was inhibited by using two approaches: 1) expression of dominant negative GTPase-impaired or proline-rich domain-deleted Dyn2 mutants; and 2) inhibition of the dynamin regulator calcineurin by cyclosporin A. In both cases, the number and extension of ECM degradation foci were drastically reduced. To understand the site and mechanism of dynamin action, the cellular structures devoted to ECM degradation were analyzed by correlative confocal light-electron microscopy. Invadopodia were found to be organized into a previously undescribed ECM-degradation structure consisting of a large invagination of the ventral plasma membrane surface in close spatial relationship with the Golgi complex. Dyn2 seemed to be concentrated at invadopodia.

Objective. To highlight the clinical profiles and angiographic findings of two patients with recurrent thunderclap headache (TCH) without subarachnoid hemorrhage (SAH) and to present modified diagnostic criteria for this unusual syndrome. Background. TCH may be a benign recurrent headache disorder or it may represent a serious underlying process such as SAH or venous sinus thrombosis. The pathophysiology of this disorder in the absence of underlying pathology is not well understood and its potential angiographic features are not well appreciated. Methods. Two case descriptions with illustrative angiography. Results. Both cases demonstrated the potential for reversible intracranial vasospasm without intracranial aneurysm or SAH and a benign clinical outcome. Conclusions. Primary TCH has a distinctive clinical and angiographic profile and must be distinguished from central nervous system vasculitis and SAH.

Hypnic headache syndrome is a rare, sleep-related, benign headache disorder. We report 19 new cases (84% females) with follow-up data. The mean age at headache onset was 60.5 ± 9 years (range 40–73 years). Headache awakened the patients from the night's sleep at a consistent time, usually between 1.00 and 3.00 a.m. (63%); three patients (16%) reported that identical headaches could occur also during daytime naps. Headache frequency was high, occurring more than 4 nights/week in 68% of the patients. Headache resolution occurred within 2 h in 68% of patients. Neurologic examination, laboratory studies, and brain imaging were unrevealing at the time of diagnosis. Headache severity largely remains unchanged or attenuates over time, but frequency may vary in either direction. Only one patient had spontaneous relief from headache. Four patients (24%) achieved permanent suppression of headache with medication, and two were able to abort individual headache attacks. Caffeine in a tablet or beverage was helpful in four patients. Lithium carbonate therapy caused side effects requiring cessation of treatment in four patients.

SUMMARYHuman membrane cofactor protein (MCP; CD46) is a widely distributed complement regulator. In the mouse, expression of MCP is largely restricted to the testis while a related, widely expressed protein (Crry) appears to perform MCP's (CD46) regulatory activity. We have developed two mouse strains transgenic for human MCP (CD46) utilizing an ∼ 400 kb YAC clone carrying the complete gene. A third mouse strain was generated using an overlapping YAC clone isolated from a second library. The expression of human MCP (CD46) in these mouse strains was characterized by immunohistochemistry, FACS, Western blotting and RT-PCR. No differences were detected in the isoform pattern or distribution among the three strains, although the expression level varied according to how many copies of the gene were integrated. The expression profile closely mimicked that observed in humans, including the same pattern of isoform expression as the donor. In addition, tissue-specific isoform expression in the kidney, salivary gland and brain paralleled that observed in man. The transgenic mice expressed low levels of MCP (CD46) on their E, in contrast to humans but in line with most other primates. These mice should be a useful tool to analyse tissue-specific expression, to establish animal models of infections and to characterize the role of MCP (CD46) in reproduction.

SUMMARY We previously described autoantibodies against a UGA serine tRNA–protein complex (tRNP(Ser)Sec) in patients with type-1 autoimmune hepatitis [1] and now define the specificity and frequency of this autoantibody and the DNA sequence encoding the tRNA(Ser)Sec-associated antigenic protein. The presence of anti-tRNP(Ser)Sec antibodies was highly specific for type-1 autoimmune hepatitis, as 47·5% of patients were positive compared with none of the control subjects. To characterize the antigenic protein(s), we immunoscreened a human cDNA library with anti-tRNP(Ser)Sec-positive sera. Two clones (19 and 13) were isolated. Clone 19 encodes a protein with a predicted molecular mass of 48·8 kD. Clone 13 is a shorter cDNA, almost identical to clone 19, which encodes a 35·9-kD protein. Expression of both cDNAs was accomplished in Escherichia coli as His-tagged recombinant proteins. Antibodies eluted from both purified recombinant proteins were able to immunoprecipitate the tRNA(Ser)Sec from a HeLa S3 cell extract, demonstrating their cross-reactivity with the mammalian antigenic complex. Recent cloning data relating to the target antigen(s) of autoantibodies in autoimmune hepatitis patients that react with a soluble liver antigen (SLA) and a liver-pancreas antigen (LP) have revealed that these two autoantibodies are identical and that the cloned antigen shows 99% amino acid sequence homology with tRNP(Ser)Sec.

SUMMARYANCA directed against PR3 are highly specific for Wegener's granulomatosis and microscopic polyangiitis, and have been implicated in the pathogenesis of small vessel vasculitis. Most PR3-ANCA are directed against conformational epitopes on PR3. This study was designed to determine whether the cleavage of the N-terminal activation dipeptide of PR3 is required for the binding of PR3-ANCA. Recombinant PR3 (rPR3) variants were expressed in the epithelial cell line, 293. As confirmed by radiosequencing, the rPR3 secreted into the 293 cell culture supernatant is N-terminally unprocessed. Two enzymatically inactive rPR3 mutants were expressed in 293 cells: rPR3-S176A and δ-rPR3-S176A. rPR3-S176A contains the N-propetide Ala-2-Glu-1, δ-rPR3-S176A does not. Culture supernatants of rPR3-S176A and δ-rPR3-S176A expressing 293 cells were used as sources of target antigen for PR3-ANCA testing by capture ELISA. Forty unselected consecutive PR3-ANCA+ sera were tested. With δ-rPR3-S176A as antigen all 40 were recognized, compared with only 34 of 40 when rPR3-S176A served as target antigen. The majority of the serum samples contained a mixture of antibodies reacting with epitopes accessible on the mature and on the proform of PR3. In conclusion, the cleavage of the N-terminal activation dipeptide of PR3 is not an absolute requirement for recognition by all PR3-ANCA. However, a substantial proportion of PR3-ANCA recognize (a) target antigen(s) exposed only after the conformational change of PR3 associated with the N-terminal processing. In 15% of sera this PR3-ANCA subset occurred exclusively. PR3-ANCA subtypes can be differentiated using specifically designed rPR3 variants as target antigens, and non-haematopoietic mammalian cells without regulated secretory pathway can be used for their expression.

Abstract Background Papillary thyroid cancer (PTC) has a generally favourable prognosis, but elderly patients with distant metastases or extracapsular invasion fair poorly. In small studies with short follow-up, young patients presenting with such extracapsular invasion and pulmonary metastases have faired well. This retrospective study was undertaken to clarify the long-term prognosis of such patients with advanced PTC. Methods Twenty-one children and young adults (median age 14 (range 6–20) years) presenting with PTC and pulmonary metastases were treated at a single institution between 1947 and 1998. Mean maximal tumour diameter was 4·65 cm. Initial surgical treatment consisted of total thyroidectomy (n = 16), subtotal thyroidectomy (n = 4) and isthmectomy (n = 1), coupled with a variety of lymph node dissections (n = 20). After operation, 19 patients were treated with ablative and incremental doses of iodine-131 until disease free. All patients were placed on suppressive thyroid hormone after operation. Mean length of follow-up was 21 years (range 3 months to 47 years). Follow-up was less than 3 years in four patients. All patients have undergone post-treatment radionucleotide and radiological evaluation. Results Nine of the 21 patients developed recurrent disease. The risk of recurrence at 5 years was 39 (95 per cent confidence interval 14–57) per cent. Eight had cervical lymph node recurrence and no patient developed recurrent pulmonary disease. All patients with identifiable recurrent disease underwent selective lymph node resection, which involved multiple resections in four. At follow-up, 18 patients remain completely free of disease, one patient has recurrent cervical node disease and two patients have died. The disease-free survival at 5 years was 95 (95 per cent confidence interval 86–100) per cent. Cause-specific death occurred in a single patient who died from extensive local disease at age 29 years after 12 years of multiple cervical lymph node recurrences. Conclusion A stepwise treatment approach including total thyroidectomy, high-dose iodine-131 treatment and early surgical reintervention for suspected local recurrent disease allows long-term survival and frequent ‘cure’ for young patients with PTC and concomitant pulmonary metastases.