Biology subjects

Alvarez Viar, G.

Publications and source records attributed to Alvarez Viar, G..

3 recordsLinked to original sources

bioRxiv2023

The Tubulin Nano-Code: a protofilament-specific pattern of tubulin post-translational modifications regulates ciliary beating mechanics

Control of ciliary beating is crucial for motility and signaling in eukaryotic cells and requires spatially restricted interactions between axonemal proteins and specific protofilaments within the ciliary microtubules. How these interactions are regulated remains poorly understood, but increasing evidence indicates that tubulin post-translational modifications (tPTMs) are required for proper ciliary motility. The Tubulin Code refers to the concept that tPTMs can modulate the function of individual microtubules in cells. Here we use a combination of immuno-cryo-electron tomography, expansion microscopy and mutant analysis to show that, in motile cilia, tubulin glycylation and polyglutamylation form mutually exclusive protofilament-specific nano-patterns at sub-microtubular scale. We show that these two nano-patterns are consistent with the distributions of axonemal dyneins and nexin-dynein regulatory complexes, respectively, and are required for their regulation during ciliary beating. Our discovery of a tubulin nano-code in cilia highlights the need of higher-resolution studies also in other cellular compartments to understand the molecular role of tPTMs. One-Sentence SummaryTubulin post-translational modifications form nanopatterns at sub-microtubular scale that enable individual protofilaments to perform specific functions Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=126 SRC="FIGDIR/small/546853v1_ufig1.gif" ALT="Figure 1"> View larger version (62K): org.highwire.dtl.DTLVardef@253704org.highwire.dtl.DTLVardef@13f0a8forg.highwire.dtl.DTLVardef@1ce673dorg.highwire.dtl.DTLVardef@1dc04e1_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2021

In situ architecture of the ciliary base reveals the stepwise assembly of IFT trains

The cilium is an antenna-like organelle that performs numerous cellular functions, including motility, sensing, and signaling. The base of the cilium contains a selective barrier that regulates the entry of large intraflagellar transport (IFT) trains, which carry cargo proteins required for ciliary assembly and maintenance. However, the native architecture of the ciliary base and the process of IFT train assembly remain unresolved. Here, we use in situ cryo-electron tomography to reveal native structures of the transition zone region and assembling IFT trains at the ciliary base. We combine this direct cellular visualization with ultrastructure expansion microscopy to describe the front-to-back stepwise assembly of IFT trains: IFT-B forms the backbone, onto which IFT-A, then dynein-1b, and finally kinesin-2 sequentially bind before entry into the cilium. One Sentence SummaryNative molecular structure of the ciliary transition zone and hierarchical order of IFT assembly visualized within Chlamydomonas cells.

cell biology↗

bioRxiv2020

The molecular structure of primary cilia revealed by cryo-electron tomography

Primary cilia are microtubule-based organelles involved in key signaling and sensing processes in eukaryotic cells. Unlike motile cilia, which have been thoroughly studied, the structure and the composition of primary cilia remain largely unexplored despite their fundamental role in development and homeostasis. They have for long been falsely regarded as simplified versions of motile cilia because they lack distinctive elements such as dynein arms, radial spokes, and central pair complex. However, revealing the detailed molecular composition and 3D structure of primary cilia is necessary in order to understand the mechanisms that govern their functions. Such structural investigations are so far being precluded by the challenging preparation of primary cilia for cryo-electron microscopy. Here, we developed an enabling method for investigating the structure of primary cilia at molecular resolution by cryo-electron tomography. We show that the well-known "9+0" arrangement of microtubule doublets is present only at the base of the primary cilium. A few microns away from the base the ciliary architecture changes into an unstructured bundle of EB1-decorated microtubule singlets and some actin filaments. Our results suggest the existence of a previously unobserved crosstalk between actin filaments and microtubules in the primary cilium. Our work provides unprecedented insights into the molecular structure of primary cilia and a general framework for uncovering their molecular composition and function in health and disease. This opens up new possibilities to study aspects of this important organelle that have so far been out of reach.

molecular biology↗