No abstract

Genetic and biochemical evidence is presented that the Exo70 subunit of the exocyst is a direct effector for both Rho3 and Cdc42 GTPases in yeast. Prenylation of these GTPases both promotes the interaction and affects the site of binding within Exo70. Thus, interaction of the Rho GTPases with Exo70 is a key event in spatial regulation of exocytosis.

Neuron-glial related cell adhesion molecule NrCAM is a newly identified negative regulator of spine density that genetically interacts with Semaphorin3F (Sema3F), and is implicated in autism spectrum disorders (ASD). To investigate a role for NrCAM in spine pruning during the critical adolescent period when networks are established, we generated novel conditional, inducible NrCAM mutant mice (Nex1Cre-ERT2: NrCAMflox/flox). We demonstrate that NrCAM functions cell autonomously during adolescence in pyramidal neurons to restrict spine density in the visual (V1) and medial frontal cortex (MFC). Guided by molecular modeling, we found that NrCAM promoted clustering of the Sema3F holoreceptor complex by interfacing with Neuropilin-2 (Npn2) and PDZ scaffold protein SAP102. NrCAM-induced receptor clustering stimulated the Rap-GAP activity of PlexinA3 (PlexA3) within the holoreceptor complex, which in turn, inhibited Rap1-GTPase and inactivated adhesive β1 integrins, essential for Sema3F-induced spine pruning. These results define a developmental function for NrCAM in Sema3F receptor signaling that limits dendritic spine density on cortical pyramidal neurons during adolescence.

Background:The mechanism by which Rab GTPases and their effectors act in tethering is not well understood. Results: An in vitro assay was developed to study vesicle clustering by the Lgl family member Sro7. Conclusion: Clustering in vitro and in vivo depends on the conformation of the Rab GTPase and Sro7. Significance: This assay provides a new tool to dissect the role of Rab and Lgl family function.

HgbA is the sole TonB-dependent receptor for hemoglobin (Hb) acquisition of Haemophilus ducreyi. Binding of Hb to HgbA is the initial step in heme acquisition from Hb. To better understand this step, we mutagenized hgbA by deletion of each of the 11 putative surface-exposed loops and expressed each of the mutant proteins in trans in host strain H. ducreyi