Tuesday, March 29, 2011

A Novel micropexophagy specific protein 'Atg35' identified in Pichia pastoris

Atg35, a micropexophagy-specific protein that regulates micropexophagic apparatus formation in Pichia pastoris
Nazarko VY et al,
Autophagy, Volume 7, Issue 4,   April 2011, Pages 375 - 385

Pexophagy can occur by two distinct pathways termed as macropexophagy and micropexophagy. In Pichia pastoris, methanol to ethanol shift causes macropexophagy while methanol to glucose shift results in peroxisome degradation by micropexophagy.

During micropexophagy, peroxisome cluster is first step-wisely surrounded by engulfing vacuole and requires a specific component called micropexophagy apparatus (MIPA) for the complete engulfment and subsequent degradation.

Using Atg28 as a bait in Yeast two hybrid screen, Authors identified a novel protein Atg35 which is micropexophagy-specific and important for efficient MIPA formation. Overexpression or deletion of this protein abolished MIPA formation without affecting other autophagic pathways. It is also observed that Atg28 bridges the interaction between Atg17 and Atg35. Authors also characterized the novel site PNS (Perinuclear Structure) where Atg35 is recruited by Atg17.

More pexophagy related recent literature -

CCZ1, MON1 and YPT7 genes are involved in pexophagy, the Cvt pathway and non-specific macroautophagy in the methylotrophic yeast Pichia pastoris
Cell Biol Int. 2011 Feb

The phosphoinositide 3-kinase Vps34p is required for pexophagy in Saccharomyces cerevisiae
Biochem J. 2011 Jan

A yeast MAPK cascade regulates pexophagy but not other autophagy pathways
J Cell Biol. 2010 Apr

Saturday, March 26, 2011

Novel yeast Peroxin identified - Pex34

The Peroxin Pex34p Functions with the Pex11 Family of Peroxisomal Divisional Proteins to Regulate the Peroxisome Population in Yeast
Robert J. Tower, Andrei Fagarasanu, John D. Aitchison, and Richard A. Rachubinski
Molecular Biology of the Cell 2011, doi:10.1091/mbc.E11-01-0084

Authors have characterized the protein encoded by YCL056c gene. Currently the protein is annotated as "Protein of unknown function" in Saccharomyces Genome Database and described as green fluorescent protein (GFP)-fusion protein localizing to the cytoplasm in a punctate pattern. (schematic image from SGD)

Authors have renamed the protein as Pex34 which is an integral peroxisomal membrane protein. Pex34 is found to be positive regulator of peroxisome population under constitutive as well as inducing conditions. Pex34 deletion led to reduced number and enlarged peroxisomes whereas overexpression led to increased peroxisome number. Authors also found interaction of pex34 with itself and other Pex11 family peroxins using yest two hybrid analysis. Notably Pex34 interacts with Fis1 but not with Vps1.

Note - Recently Pex33 was identified from Neurospora crassa
Identification of PEX33, a novel component of the peroxisomal docking complex in the filamentous fungus Neurospora crassa
Managadze D et al.

Thursday, March 10, 2011

PhD position: Control of peroxisome abundance in metabolic diseases & cancer

Employer : Institute of Cell Biology, ETH Zurich, Switzerland
Website : http://www.cell.biol.ethz.ch
Last date of application : April 15, 2011

Interested applicants should email their CV, short statement of research interests(half page), and names of 2 referees by email to: Werner.kovacs@cell.biol.ethz.ch
Or by using Online application link

Our research interests are on the genetic and biochemical mechanisms underlying the control of peroxisome abundance in metabolic diseases and cancer. Peroxisomes are highly versatile and dynamic organelles whose number, size and function are vastly dependent on the cell type and growth conditions. The abundance of peroxisomes within a cell is dynamically controlled by environmental cues and (patho)physiological conditions. We apply a wide range of experimental cues technologies (e.g. live-cell imaging, RNAi-screening, functional genomics, proteomics, metabolomics) and model disease states in the mouse.

The successful candidate will be enrolled in the Ph.D. Program of the Life Science Zurich Graduate School. The position is located in Science City, the Life Science Campus of ETH Zurich. The research campus offers state-of-the-art facilities for advanced light and electron microscopy, high-throughput, image-based RNAi screening, quantitative proteomics, functional genomics, and computational analysis of large data-sets.

For further scientific information please contact: werner.kovacs@cell.biol.ethz.ch (http://www.cell.biol.ethz.ch/research/krek/group_members/kovacsw/index).

Dr. Werner Kovacs
ETH Zürich
Institute of Cell Biology
Schafmattstrasse 18, HPM F39
CH-8093 Zürich, Switzerland

Tuesday, March 8, 2011

New Paper - Study on Pex5 ancillary binding site for SCP2

The Peroxisomal Targeting Signal 1 in sterol carrier protein 2 is autonomous and essential for receptor recognition
Williams CP et al.
BMC Biochemistry 2011, 12:12
Published: 4 March 2011
Brief Summary - Authors studied the second, ancillary receptor-cargo binding site in Pex5 for the PTS1 protein SCP2 distinct from the PTS1 itself. Point mutation in Pex5 were done to check the effects on Pex5-SCP2 binding which was found to be moderately reduced in binding assays but the effect was not visible using in vivo localisation assays. Authors conclude that the second binding site in Pex5 is not essential for at least SCP2 indicating PTS1 is alone sufficient for its peroxisomal targeting.

Mutations within the ancillary SCP2 binding site of Pex5p do not impair peroxisomal import

PTS1 of SCP2 is essential and sufficient for peroxisomal targeting

(Thanks to Biomedcentral BMC, Open Access Publisher for the open access policy)