ERdj5 Reductase Cooperates with Protein Disulfide Isomerase To Promote Simian Virus 40 Endoplasmic Reticulum Membrane Translocation.

Unlabelled: The nonenveloped polyomavirus (PyV) simian virus 40 (SV40) traffics from the cell surface to the endoplasmic reticulum (ER), where it penetrates the ER membrane to reach the cytosol before mobilizing into the nucleus to cause infection. Prior to ER membrane penetration, ER lumenal factors impart structural rearrangements to the virus, generating a translocation-competent virion capable of crossing the ER membrane. Here we identify ERdj5 as an ER enzyme that reduces SV40's disulfide bonds, a reaction important for its ER membrane transport and infection.

Paclitaxel-conjugated PAMAM dendrimers adversely affect microtubule structure through two independent modes of action.

Paclitaxel (Taxol) is an anticancer drug that induces mitotic arrest via microtubule hyperstabilization but causes side effects due to its hydrophobicity and cellular promiscuity. The targeted cytotoxicity of hydrophilic paclitaxel-conjugated polyamidoamine (PAMAM) dendrimers has been demonstrated in cultured cancer cells. Mechanisms of action responsible for this cytotoxicity are unknown, that is, whether the cytotoxicity is due to paclitaxel stabilization of microtubules, as is whether paclitaxel is released intracellularly from the dendrimer.

Luminal localization of α-tubulin K40 acetylation by cryo-EM analysis of fab-labeled microtubules.

The αβ-tubulin subunits of microtubules can undergo a variety of evolutionarily-conserved post-translational modifications (PTMs) that provide functional specialization to subsets of cellular microtubules. Acetylation of α-tubulin residue Lysine-40 (K40) has been correlated with increased microtubule stability, intracellular transport, and ciliary assembly, yet a mechanistic understanding of how acetylation influences these events is lacking. Using the anti-acetylated tubulin antibody 6-11B-1 and electron cryo-microscopy, we demonstrate that the K40 acetylation site is located inside the microtubule lumen and thus cannot directly influence events on the microtubule surface, including kinesin-1 binding.

Ligand-induced architecture of the leptin receptor signaling complex.

Despite the crucial impact of leptin signaling on metabolism and body weight, little is known about the structure of the liganded leptin receptor (LEP-R) complex. Here, we applied single-particle electron microscopy (EM) to characterize the architecture of the extracellular region of LEP-R alone and in complex with leptin. We show that unliganded LEP-R displays significant flexibility in a hinge region within the cytokine homology region 2 (CHR2) that is connected to rigid membrane-proximal FnIII domains.

High-aspect ratio nanochannel formation by single femtosecond laser pulses.

Single femtosecond pulsed laser damage can be confined radially to regions smaller than the focus spot size due to the highly nonlinear mechanisms for energy absorption and ablation in transparent dielectrics. Along the propagation axis, however, we show that channels can be machined much deeper than the Rayleigh range of the laser focus. Using focused ion beam cross sections and acetate imprints, we analyze these channels and show that spherical aberration is not the primary source for this elongated damage, which is likely caused by microscale filamentation.

Novel morphologies and non-linear scaling of laser damage in glass by tightly-focused femtosecond pulses.

We examine the relationship between pulse energy and the morphology of damage in glass, produced by a tightly-focused femtosecond pulsed laser. For fluences up to three times that of threshold, an unexpected discontinuity in the scaling of damage size is caused by ejection of rings of material surrounding central damage that appear above a sharp threshold fluence. A mechanism for the production of these structures via thermal expansion and shockwave generation is proposed.