Lamellipodium extension and membrane ruffling require different SNARE-mediated trafficking pathways

Background

Intracellular membrane traffic is an essential component of the membrane remodeling that supports lamellipodium extension during cell adhesion. The membrane trafficking pathways that contribute to cell adhesion have not been fully elucidated, but recent studies have implicated SNARE proteins. Here, the functions of several SNAREs (SNAP23, VAMP3, VAMP4 and syntaxin13) are characterized during the processes of cell spreading and membrane ruffling.

Results

We report the first description of a SNARE complex, containing SNAP23, syntaxin13 and cellubrevin/VAMP3, that is induced by cell adhesion to an extracellular matrix. Impairing the function of the SNAREs in the complex using inhibitory SNARE domains disrupted the recycling endosome, impeded delivery of integrins to the cell surface, and reduced haptotactic cell migration and spreading. Blocking SNAP23 also inhibited the formation of PMA-stimulated, F-actin-rich membrane ruffles; however, membrane ruffle formation was not significantly altered by inhibition of VAMP3 or syntaxin13. In contrast, membrane ruffling, and not cell spreading, was sensitive to inhibition of two SNAREs within the biosynthetic secretory pathway, GS15 and VAMP4. Consistent with this, formation of a complex containing VAMP4 and SNAP23 was enhanced by treatment of cells with PMA. The results reveal a requirement for the function of a SNAP23-syntaxin13-VAMP3 complex in the formation of lamellipodia during cell adhesion and of a VAMP4-SNAP23-containing complex during PMA-induced membrane ruffling.

Conclusions

Our findings suggest that different SNARE-mediated trafficking pathways support membrane remodeling during ECM-induced lamellipodium extension and PMA-induced ruffle formation, pointing to important mechanistic differences between these processes.

The CVC removal distress syndrome: an unappreciated complication of central venous catheter removal

The removal of a central venous catheter (CVC) can be complicated by rare but potentially life-threatening neurocardiopulmonary distress. The clinical courses of eight patients who had CVC removal complications are reviewed. Seven patients had catheter removal from the right internal jugular vein, and one from the right subclavian vein. The complications occurred after complete removal of the catheter (four patients), after guidewire replacement for catheter change (three patients), and after detachment of the hemostasis side port of the Swan introducer during sheath removal (one patient). Each of them had more than one complication. The major complications were: neurologic paresis or coma (four patients), respiratory failure (four patients), and shock (two patients). One patient died of pulmonary sepsis. The overall mortality rate was 12.5 per cent. Guidelines for safe removal of central venous catheters are proposed. Possible mechanisms of the complications are discussed. We refer to the observed complications as the CVC removal distress syndrome.

Sleeve lobectomy, segmentectomy, and thoracoscopy in the management of carcinoma of the lung

In patients with lung cancer, the goals of limited resection procedures of the lung and major airways are to provide an adequate cancer operation while preserving functioning lung tissue. Discussed in this article are sleeve lobectomy, an alternative to pneumonectomy in patients with cancer in a lobar orifice; segmentectomy or wedge resection, an alternative to lobectomy in those with a peripheral lung cancer; and thoracoscopy, an alternative to open thoracotomy for various chest malignancies.

When the suggestion box fails

Make a guess: Would a company that needs the work-improvement ideas of employees, but whose experience with the use of a suggestion box has been less than successful, obtain more and better quality ideas by enlisting the participation of its employees or by assigning them an idea quota? Donald W. Myers and Earnest R. Archer report the experience of a company that tried both approaches--participative and authoritative--and, surprisingly, in a world where participation is the magic formula, the group assigned a quota produced more and better ideas than did the participatory group.