Intersectin‐1s (ITSN‐1s), a five Src homology 3 (SH3) domain‐containing protein, is critically required for caveolae and clathrin‐mediated endocytosis (CME), due to its interactions with dynamin (dyn). Of the five SH3A‐E domains, SH3A is unique because of its high affinity for dyn and potent inhibition of CME. However, the molecular mechanism by which SH3A integrates in the overall function of ITSN‐1s to regulate the endocytic process is not understood. Using biochemical and functional approaches as well as high‐resolution electron microscopy, we show that SH3A exogenously expressed in human lung endothelial cells caused abnormal endocytic structures, distorted caveolae clusters, frequent staining‐dense rings around the caveolar necks and 60% inhibition of caveolae internalization. In vitro studies further revealed that SH3A, similar to full‐length ITSN‐1s stimulates dyn2 oligomerization and guanosine triphosphatase (GTP)ase activity, effects not detected when other SH3 domains of ITSN‐1s were used as controls. Strikingly, in the presence of SH3A, dyn2–dyn2 interactions are stabilized and despite continuous GTP hydrolysis, dyn2 oligomers cannot disassemble. SH3A may hold up caveolae release from the plasma membrane and formation of free‐transport vesicles, by prolonging the lifetime of assembled dyn2. Altogether, our results indicate that ITSN‐1s, via its SH3A has the unique ability to regulate dyn2 assembly–disassembly and function during endocytosis.
We present measurements of net charge fluctuations in Au + Au collisions at $\sqrt {s_{NN} } $ = 19.6, 62.4, 130, and 200 GeV, Cu + Cu collisions at $\sqrt {s_{NN} } $ = 62.4, 200 GeV, and p + p collisions at $\sqrt s $ = 200 GeV using the net charge dynamical fluctuations measure ν+ −,dyn. The dynamical fluctuations are non-zero at all energies and exhibit a rather modest dependence on beam energy. We find that at a given energy and collision system, net charge dynamical fluctuations violate 1/Nch scaling, but display approximate 1/Npart scaling. We observe strong dependence of dynamical fluctuations on the azimuthal angular range and pseudorapidity widths.