In many brain regions, gephyrin and GABA A receptor clustering at developing inhibitory synapses depends on the guanine nucleotide exchange factor collybistin (Cb). The vast majority of Cb splice variants contain an autoinhibitory src homology 3 domain, and several synaptic proteins are known to bind to this SH3 domain and to thereby activate gephyrin clustering. However, many functional GABAergic synapses form independently of the known Cb-activating proteins, indicating that additional Cb activators must exist. Here we show that the small Rho-like GTPase TC10 stimulates Cb-dependent gephyrin clustering by binding in its active, GTP-bound state to the pleckstrin homology domain of Cb. Overexpression of a constitutively active TC10 variant in neurons causes an increase in the density of synaptic gephyrin clusters and mean miniature inhibitory postsynaptic current amplitudes, whereas a dominant negative TC10 variant has opposite effects. The enhancement of Cb-induced gephyrin clustering by GTP-TC10 does not depend on the guanine nucleotide exchange activity of Cb but involves an interaction that resembles reported interactions of other small GTPases with their effectors. Our data indicate that GTP-TC10 activates the major src homology 3 domain-containing Cb variants by relieving autoinhibition and thus define an alternative GTPase-driven signaling pathway in the genesis of inhibitory synapses.RhoQ | Cdc42 | postsynaptic scaffold | synaptogenesis | neuroligin

Protein ubiquitination is a core regulatory determinant of neural development. Previous studies have indicated that the Nedd4-family E3 ubiquitin ligases Nedd4-1 and Nedd4-2 may ubiquitinate phosphatase and tensin homolog (PTEN) and thereby regulate axonal growth in neurons. Using conditional knockout mice, we show here that Nedd4-1 and Nedd4-2 are indeed required for axonal growth in murine central nervous system neurons. However, in contrast to previously published data, we demonstrate that PTEN is not a substrate of Nedd4-1 and Nedd4-2, and that aberrant PTEN ubiquitination is not involved in the impaired axon growth upon deletion of Nedd4-1 and Nedd4-2. Rather, PTEN limits Nedd4-1 protein levels by modulating the activity of mTORC1, a protein complex that controls protein synthesis and cell growth. Our data demonstrate that Nedd4-family E3 ligases promote axonal growth and branching in the developing mammalian brain, where PTEN is not a relevant substrate. Instead, PTEN controls neurite growth by regulating Nedd4-1 expression.

No abstract

Flexible bronchoscopy (FB) is commonly performed by respiratory physicians for diagnostic as well as therapeutic purposes. However, bronchoscopy practices vary widely across India and worldwide. The three major respiratory organizations of the country supported a national-level expert group that formulated a comprehensive guideline document for FB based on a detailed appraisal of available evidence. These guidelines are an attempt to provide the bronchoscopist with the most scientifically sound as well as practical approach of bronchoscopy. It involved framing appropriate questions, review and critical appraisal of the relevant literature and reaching a recommendation by the expert groups. The guidelines cover major areas in basic bronchoscopy including (but not limited to), indications for procedure, patient preparation, various sampling procedures, bronchoscopy in the ICU setting, equipment care, and training issues. The target audience is respiratory physicians working in India and well as other parts of the world. It is hoped that this document would serve as a complete reference guide for all pulmonary physicians performing or desiring to learn the technique of flexible bronchoscopy.