Lab Members

Randy Schekman
schekman@berkeley.edu

A brief biography of Randy is available on the HHMI website.

Lazar Dimitrov (post-doc)
dimitrovl@berkeley.edu

Peroxisomes are important organelles in virtually all eukaryotic cells and essential for normal human development. There has been considerable controversy in the field about the targeting of peroxisomal membrane proteins (PMPs). Recent studies from our lab demonstrate that PMPs originate from the ER by a vesicle budding process. I am using Saccharomyces cerevisiae as a model system and taking several genetic approaches to uncover novel factors involved in pre-peroxisomal vesicle budding from the ER.

Alexandre Fernandes (post-doc)
afernandes@berkeley.edu

Wnt proteins are small secreted proteins present in all animal genomes and involved in embryonic development and adult homeostasis. While the Wnt-induced signal transduction cascades are well studied, the mechanisms underlying Wnt secretion present interesting challenges. The goal of my research is to identify the ARF family members and their effectors necessary for the traffic of Wnt from the trans-Golgi network to the cell surface, using a siRNA approach and a subsequent biochemical reconstitution assay.

Liang Ge (post-doc)
lge19830626@gmail.com

Autophagy is a fundamental intracellular transport pathway, and is considered to be an essential pro-survival process in stress conditions. Although the origin of the autophagosome has been a subject of intense study, it has been difficult to resolve using current imaging techniques. I plan to establish an in vitro autophagosome formation assay to assist in answering this question and to characterize the newly formed autophagosomes, so as to gain insight into autophagy initiation and regulation.

Amita Gorur (grad student)
agorur@lbl.gov

The molecular underpinnings of procollagen trafficking in cells has confounded cell biologists for decades. Recent work has shown that mono-ubiquitination of Sec31 by the ubiquitin ligase complex Cul3-Klhl12 leads to the formation of enlarged vesicles that drive the secretion of collagen. My goal is to understand the role of these vesicles in collagen transport.

Yusong Guo (post-doc)
guoy@berkeley.edu

Planar cell polarity (PCP), a process in which the epithelial tissues are polarized within the plane of the epithelium, is controlled by a group of conserved signaling molecules including Frizzled and Vangl2. My research is focused on identifying the Arf family members and their effectors that are required for sorting of Frizzled and Vangl2 at the trans Golgi network, using an siRNA knockdown approach and a biochemical reconstitution assay.

Florian Koban (visiting grad student)
florian.koban@meduniwien.ac.at

The serotonin transporter (SERT) in our brain is responsible for the reuptake of serotonin from the synaptic cleft. This leads to termination of the signals elicited by this neurotransmitter. Susceptibility to development of mood disorders (e.g., depression) is significantly affected by SERT function. ER export of SERT exclusively relies on a COPII protein complex containing SEC24C. I will use a COPII vesicle budding assay combined with site directed mutagenesis of SERT and SEC24C to understand the specific interaction between both proteins.

Jason Lam (post-doc)
zasonlam@gmail.com

Peroxisomes are ubiquitous eukaryotic organelles which serve in beta-oxidation of fatty acids, hydrogen peroxide-based respiration and oxidative stress defense. In my study, an in vitro vesicle formation assay will be set up to identify ER-derived pre-peroxisomal vesicles. Furthermore the molecular mechanism will be studied by fractionating any cytosolic proteins (e.g. Pex19) required for budding of pre-peroxisomal vesicles.

Bob Lesch (lab manager)
lesch@berkeley.edu

David Melville (post-doc)
afroginawell@gmail.com

Sar1, one of the five core COPII components, is a highly conserved small GTPase. Mammals have two paralogs of Sar1, SAR1A and SAR1B, which share 90% sequence identity. Despite their high similarity, it has been found that mutations in SAR1B, but not SAR1A, are associated with Chylomicron retention disease in humans. I am using a lipid secreting rat cell line to illuminate the paralog specific functions of Sar1 and the relationship between Sar1 and the COPII outer coat.

Claudia Morales (lab assistant)
moralesacg@yahoo.com

Ryan Morrie (grad student)
ryan.morrie@berkeley.edu

I am determining whether the YYXXF sorting motif on the C-terminal cytoplasmic domain of Vangl2 is sufficient for transmembrane proteins to be sorted into vesicles that bud from the trans Golgi network in an Arfrp1 and AP-1 dependent manner. Specifically, I will be swapping the C-terminal cytoplasmic domains of Vangl2 and its oppositely localized PCP counterpart Frizzled-6 and assaying both their localization to the plasma membrane and in vesicles budding from the trans Golgi.

Lelio Orci (collaborator)
lelio.orci@medecine.unige.ch

Kanika Pahuja (née Bajaj) (post-doc)
kanika@berkeley.edu

My research involves exploring the possible existence of large flexible COPII vesicles to accommodate large secretory cargo molecules like chylomicrons and procollagen. More specifically, I am trying to reconstitute the in vitro vesicle budding of Procollagen-I from the ER of mammalian cells.

Matt Shurtleff (grad)
shurtleff.matthew@gmail.com

Exosomes are 70-100 nm vesicles that are released extracellularly upon fusion of the multivesicular body with the plasma membrane. Recently, these vesicles have been recognized as signaling vehicles in various normal and pathological conditions. Despite growing interest in exosomes, the molecular mechanisms governing selective packaging of molecular cargo remain undefined. I am seeking to understand how miRNAs are generally enriched in exosomes and how specific miRNAs are selectively packaged.

Peggy McCutchan Smith (administrative assistant)
magsmith@berkeley.edu

Lixon Wang (undergrad)
lixonwang@gmail.com

Peroxisomes perform a number of important cellular functions, including the degradation of fatty acids by beta oxidation. Despite their biochemical importance, the process of forming these organelles is not fully understood. My project is to explore the role of the endoplasmic reticulum in peroxisome biogenesis using the model organism Saccharomyces cerevisiae.

Ryan Wang (undergrad)
ryan.wang@berkeley.edu

Planar Cell Polarity (PCP) plays a key role in many vertebrate developmental processes and is controlled by a group of signaling receptors. My research focuses on the signaling receptor Frizzled and identifying the Arf proteins and effectors involved in the trafficking of Frizzled at the trans-Golgi using siRNA knockdown assays.

Livy Wilz (grad student)
lwilz@berkeley.edu

Autophagy is a critical cellular homeostasis pathway that allows the cell to respond to nutritional stress. I am interested in how autophagy activity is regulated and how this regulation is translated into autophagosome formation. To do this, I am focusing on understanding how the the autophagy-specific PI3 kinase complex regulates this process. This involves using a recently established in vitro autophagy assay to characterize the role that each complex component plays in autophagy initiation.

Zong Wu (undergrad)
davidzywu@gmail.com

Membrane and secreted proteins enter the endoplasmic reticulum and are transported through the secretory pathway to their final destination, which includes the Golgi complex, peroxisomes, lysosomes, and the cell surface. The goal of my project is to study the factors that regulate the transport of cargos from the trans-Golgi network to the cell surface using an siRNA knockdown assay.

Lin Yuan (grad student)
linyuan@berkeley.edu

Collagen is the most abundant protein in mammals and it functions to maintain tissue integrity. It is secreted by the cell via the COPII mediated secretory pathway. I am interested in learning how the rigid procollagen fibers that are 300nm in length are packaged into COPII vesicles that are typically 60nm in diameter.

Min Zhang (post-doc)
minzhang@berkeley.edu

Mammalian cells secrete proteins mainly through the conventional ER–Golgi secretory pathway. However, some cytoplasmic proteins are released in an unconventional manner independent of ER and Golgi. Autophagy, a cellular process characterized by de novo formation of double membrane structures for intracellular material degradation, contributes to one aspect of unconventional secretion, such as the secretion of IL-1beta. However, the molecular mechanism of autophagy-mediated protein secretion is unclear. Using IL-1beta as a marker, I plan to establish a cell-free system to uncover the mechanisms autophagy-related unconventional secretion.

Pengcheng Zhang (grad student)
pczhang@berkeley.edu

In mammals, Vangl2 is an important protein for the proper development of the neural tube. Mislocalization of this protein leads to defects in the development of the neural tube and other tissues. My project focuses on examining the role of Dishevelled in the ER export of Vangl2.