| |
Sharon
has been working with Max Summers for 14 years. She performed some of
the initial work identifying proteins of the occluded derived virus. She
has been intimately involved in virtually all of the studies on ODV since.
While students, staff and other personnel come and go, Sharon serves as
the collective memory for the historical development of projects, clones
and no one in the lab can find a reagent faster than she can!
Sharon is the person who helps new staff and student get oriented, and
who directs and problem solves laboratory activities on a daily basis.
Current Research Projects:
MECHANISM OF TRAFFICKING OF INTEGRAL MEMBRANE PROTEINS FROM THE ENDOPLASMIC
RETICULUM TO THE INNER NUCLEAR MEMBRANE.
Background: Mutations within a number of
resident inner nuclear membrane (INM) proteins are known to cause human
diseases, including several types of muscular and lipid dystrophies. Knowledge
of function, protein and lipid composition, mechanisms of protein sorting,
and trafficking to the INM are not well defined. It is proposed that resident
integral membrane proteins traffic to the INM by diffusion-retention.
By this model, INM integral membrane proteins freely diffuse between the
endoplasmic reticulum (ER), outer nuclear membrane (ONM) and INM. Interactions
with nucleoplasmic components anchor these proteins at the INM, thus removing
them from the diffusible pool. While this model fits basic characteristics
of some INM proteins, it does not explain enrichment at the INM of other
resident proteins. Recent studies have increased our knowledge from less
than 10 to more than 67 INM proteins. For some of these, the retention
domain can be removed and the truncated protein still enriches at the
INM. Other INM proteins do not contain a discernable retention domain.
Thus it is our hypothesis that diffusion/retention is not the only mechanism
for protein sorting, trafficking and enrichment at the INM.
Many viral processes mimic cellular mechanisms and pathways. This feature,
along with the property of viruses to provide a synchronous, amplified
pulse of unique viral integral membrane proteins trafficking to specific
organelles has resulted in kinetic descriptions and detailed knowledge
of many aspects of cellular protein trafficking. Baculovirus provides
an amplified pulse of viral envelope proteins which transit from their
site of insertion at the ER to the ONM and INM, and finally to membrane
vesicles that form within the infected cell nucleus. Thus, this virus
provides a powerful tool to study the pathway of integral membrane proteins
to the INM. These same viral proteins are enriched at the nuclear envelope
and INM in the absence of infection in both insect and mammalian cells.
This suggests that the mechanism(s) that regulates trafficking to the
INM are not unique to the virus.
Specific Aims: The long-range
goal is to understand the mechanism of integral membrane protein sorting
and trafficking to the INM. The goal of this project is to discern the
mechanism utilized by baculovirus envelope proteins as they traverse the
INM on their way to viral-induced membranes within the nucleus. At every
stage we will compare the mechanism(s) utilized by viral membrane proteins
with mammalian INM proteins. Thus, both viral and cellular INM protein
markers will be utilized to test the hypothesis that more than one mechanism
functions during trafficking to the INM. It is our expectation that significant
insights on the biochemistry of protein trafficking to the INM will be
revealed during these studies.
The integral membrane protein ODV-E66 is the primary viral marker used
throughout this study. This was chosen because a minimal amino acid sequence
(33 amino acids) sufficient for trafficking to the ODV envelope has been
identified within this protein. This minimal sequence has distinctive
characteristics that are present on both viral envelope and mammalian
INM proteins; these features are named the Signature Motif (SM). The mammalian
resident INM proteins lamin B receptor (LBR) and nurim have been chosen
for comparison to the viral marker. LBR, the most characterized INM protein,
is representative of a larger group of INM proteins. Nurim represents
a second class of INM proteins, with features significantly different
from those represented by LBR.
Research Plan: Our experimental strategy
is to use the viral protein ODV-E66 and SM-fusions to investigate potential
sites of regulation in the pathway to the nuclear membrane. Special attention
is directed to the first putative sites of regulation: 1) sorting at the
time of primary translocation across the endoplasmic reticulum; 2) specific
transport from the ER to the outer nuclear membrane and; 3) potential
interaction with proteins of the nuclear pore complex as the protein traverses
from the ONM to the INM. Our strategy involves cross-linking and identification
of proteins in close proximity during these intermediate phases. With
identity of potential partners determined, mutational analysis will be
used to determine if the putative partners function during the trafficking
process.
Personal Interests and Hobbies:
Sharon shares her life with
the 120 lb. Canadian timberwolf named Koko.
So much of her spare time is devoted to "pack activities" which
include unique human/canine versions of soccer, chase, fetch and grooming.
When not "wolfing around" Sharon is an avid seamstress and shares
quiltmaking activities with her 102 year old grandmother. She is an amateur
photographer who spends a great deal of time in her home darkroom. Other
activities include
rose gardening, and home renovation.
|
|
