Pitstop-2 and its novel derivative RVD-127 disrupt global cell dynamics and nuclear pores integrity by direct interaction with small GTPases

Clathrin-mediated endocytosis (CME) is an essential cell physiological process of broad biomedical relevance. Since the recent introduction of Pitstop-2 as a potent CME inhibitor, we and others have reported on substantial clathrin-independent inhibitory effects. Herein, we developed and experimentally validated a novel fluorescent derivative of Pitstop-2, termed RVD-127, to clarify Pitstop-2 diverse effects. Using RVD-127, we were able to trace additional protein targets of Pitstop-2. Besides inhibiting CME, Pitstop-2 and RVD-127 proved to directly and reversibly bind to at least two members of the small GTPase superfamily Ran and Rac1 with particularly high efficacy. Binding locks the GTPases in a guanosine diphosphate (GDP)-like conformation disabling their interaction with their downstream effectors. Consequently, overall cell motility, mechanics and nucleocytoplasmic transport integrity are rapidly disrupted at inhibitor concentrations well below those required to significantly reduce CME. We conclude that Pitstop-2 is a highly potent, reversible inhibitor of small GTPases. The inhibition of these molecular switches of diverse crucial signaling pathways, including nucleocytoplasmic transport and overall cell dynamics and motility, clarifies the diversity of Pitstop-2 activities. Moreover, considering the fundamental importance and broad implications of small GTPases in physiology, pathophysiology and drug development, Pitstop-2 and RVD-127 open up novel avenues.

Use of tissue expansion to facilitate liver and small bowel transplant in young children with contracted abdominal cavities

Liver and small bowel transplant is an established treatment for infants with IFALD. Despite organ reduction techniques, mortality on the waiting list remains high due to shortage of size-matched pediatric donors. Small abdominal cavity volume due to previous intestinal resection poses a significant challenge to achieve abdominal closure post-transplant. Seven children underwent tissue expansion of abdominal skin prior to multiorgan transplant. In total, 17 tissue expanders were placed subcutaneously in seven children. All seven subjects underwent re-exploration to deal with complications: hematoma, extrusion, infection, or port related. Three expanders had to be removed. Four children went on to have successful combined liver and small bowel transplant. Two children died on the waiting list of causes not related to the expander and one child died from sepsis attributed to an infected expander. Tissue expansion can generate skin to facilitate closure of abdomen post-transplant, thus allowing infants with small abdominal volumes to be considered for transplant surgery. Tissue expansion in children with end-stage liver disease and portal hypertension is associated with a very high complication rate and needs to be closely monitored during the expansion process.

Syndactyly correction: an aesthetic reconstruction

Various flaps have been used with and without skin grafts to separate digits with syndactyly. Dorsal flap techniques with and without grafts result in dorsal and thus more visible scars. Some of the recent techniques which use no grafts are only applicable for some simple syndactylies. The technique described in this paper uses a combination of techniques which have been described previously. A shaped palmar flap is used to create the web space; narrow V-flaps and full-thickness skin grafts are used to resurface the lateral defects on the fingers and reciprocal pulp flaps are used to create aesthetically pleasing nail folds. This technique allows the full thickness grafts to be hidden on the radial and ulnar sides of the fingers and palm. It increases the span of the hand in conditions where there is shortage of palmar skin. A retrospective review has been undertaken of 102 patients in whom 221 webs were reconstructed through 176 surgical procedures. There were 54 cases of simple syndactylies (53%) and the rest were complex. Complications were encountered in 11 operations (6%) and web creep was noted in 12 web spaces (5%). Re-operation for web creep has been carried out in seven web spaces (3%).