Table of Contents

Volume 2, Issue 5

  September/October 2012

  Pages 143 - 188

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Open Access Article

Intravital microscopy: A practical guide on imaging intracellular structures in live animals

Andrius Masedunskas, Oleg Milberg, Natalie Porat-Shliom, Monika Sramkova, Tim Wigand, Panomwat Amornphimoltham and Roberto Weigert
Pages 143 - 157
http://dx.doi.org/10.4161/bioa.21758
Abstract | Full Text | PDF

Intravital microscopy is an extremely powerful tool that enables imaging several biological processes in live animals. Recently, the ability to image subcellular structures in several organs combined with the development of sophisticated genetic tools has made possible extending this approach to investigate several aspects of cell biology. Here we provide a general overview of intravital microscopy with the goal of highlighting its potential and challenges. Specifically, this review is geared toward researchers that are new to intravital microscopy and focuses on practical aspects of carrying out imaging in live animals. Here we share the know-how that comes from first-hand experience, including topics such as choosing the right imaging platform and modality, surgery and stabilization techniques, anesthesia and temperature control. Moreover, we highlight some of the approaches that facilitate subcellular imaging in live animals by providing numerous examples of imaging selected organelles and the actin cytoskeleton in multiple organs.

Open Access Article

Myosins in cell junctions

Katy C. Liu and Richard E. Cheney
Pages 158 - 170
http://dx.doi.org/10.4161/bioa.21791
Abstract | Full Text | PDF

The development of cell-cell junctions was a fundamental step in metazoan evolution, and human health depends on the formation and function of cell junctions. Although it has long been known that actin and conventional myosin have important roles in cell junctions, research has begun to reveal the specific functions of the different forms of conventional myosin. Exciting new data also reveals that a growing number of unconventional myosins have important roles in cell junctions. Experiments showing that cell junctions act as mechanosensors have also provided new impetus to understand the functions of myosins and the forces they exert. In this review we will summarize recent developments on the roles of myosins in cell junctions.




COMMENTARIES

Open Access Article

Competition and compensation: Dissecting the biophysical and functional differences between the class 3 myosin paralogs, myosins 3a and 3b

Uri Manor, M'hamed Grati, Christopher M. Yengo, Bechara Kachar and Nir S. Gov
Pages 171 - 174
http://dx.doi.org/10.4161/bioa.21733
Abstract | Full Text | PDF

Stereocilia are actin protrusions with remarkably well-defined lengths and organization. A flurry of recent papers has reported multiple myosin motor proteins involved in regulating stereocilia structures by transporting actin-regulatory cargo to the tips of stereocilia.^1-13 In our recent paper, we show that two paralogous class 3 myosins — Myo3a and Myo3b — both transport the actin-regulatory protein Espin 1 (Esp1) to stereocilia and filopodia tips in a remarkably similar, albeit non-identical fashion.¹ Here we present experimental and computational data that suggests that subtle differences between these two proteins’ biophysical and biochemical properties can help us understand how these myosin species target and regulate the lengths of actin protrusions.

Open Access Article

Tethering factor P115: A new model for tether-SNARE interactions

Robert Grabski, Jesse Hay and Elizabeth Sztul
Pages 175 - 180
http://dx.doi.org/10.4161/bioa.21702
Abstract | Full Text | PDF

The membrane tethering factor p115 has been shown to have important functions in ER to Golgi traffic and Golgi biogenesis. The multidomain structure of p115 allows for interactions with a diverse array of proteins that govern cargo movement at the ER-Golgi interface. Within its C-terminal region p115 contains four coiled-coil domains (CC1-CC4). Of the four coiled-coils, only CC1 has been shown to be required for p115 function, presumably by its ability to bind numerous SNARE proteins as well as the small GTPase Rab1. Recently, we showed that CC4 also interacts with SNARE proteins and that CC4 is required for p115 function in Golgi homeostasis and the trafficking of transmembrane but not soluble cargo. Here, we propose a novel model wherein p115 facilitates membrane tethering and fusion by simultaneously engaging its CC1 and CC4 domains with distinct SNARE proteins to promote formation of SNARE complexes.




SHORT COMMUNICATION

Open Access Article

How a common variant in the growth factor receptor gene, NTRK1, affects white matter

Meredith N. Braskie, Neda Jahanshad, Arthur W. Toga, Katie L. McMahon, Greig I. de Zubicaray, Nicholas G Martin, Margaret J. Wright and Paul M. Thompson
Pages 181 - 184
http://dx.doi.org/10.4161/bioa.22190
Abstract | Full Text | PDF

Growth factors and their receptors are important for cellular migration as well as axonal guidance and myelination in the brain. They also play a key role in programmed cell death, and are implicated in a number of mental illnesses. Recently, we reported that healthy young adults who carry the T allele variant in the growth factor gene, NTRK1 (at location rs6336), had lower white matter integrity than non-carriers on diffusion images of the brain. Diffusion tensor imaging (DTI) revealed how this single nucleotide polymorphism affects white matter microstructure in human populations; DTI is also used to identify characteristic features of brain connectivity in typically developing children and in patients. Newly discovered links between neuroimaging measures and growth factors whose molecular neuroscience is well known offer an important step in understanding mechanisms that contribute to brain connectivity. Altered fiber connectivity may mediate the relationship between some genetic risk factors and a variety of mental illnesses.




RESEARCH PAPER

Open Access Article

The juxtamembrane domain of the E-cadherin cytoplasmic tail contributes to its interaction with Myosin VI

Sabine Mangold, Suzanne J. Norwood, Alpha Yap and Brett M. Collins
Pages 185 - 188
http://dx.doi.org/10.4161/bioa.22082
Abstract | Full Text | PDF

We recently identified the atypical myosin, Myosin VI, as a component of epithelial cell-cell junctions that interacts with E-cadherin. Recombinant proteins bearing the cargo-binding domain of Myosin VI (Myo VI-CBD) or the cytoplasmic tail of E-cadherin can interact directly with one another. In this report we further investigate the molecular requirements of the interaction between Myo VI-CBD and E-cadherin combining truncation mutation analysis with in vitro binding assays. We report that a short (28 amino acid) juxtamembrane region of the cadherin cytoplasmic tail is sufficient to bind Myo VI-CBD. However, central regions of the cadherin tail adjacent to the juxtamembrane sequence also display binding activity for Myo VI-CBD. It is therefore possible that the cadherin tail bears two binding sites for Myosin VI, or an extended binding site that includes the juxtamembrane region. Nevertheless, our biochemical data highlight the capacity for the juxtamembrane region to interact with functionally-significant cytoplasmic proteins.