Current
Volume 3, Number 1, 2003
Contents
The Study of HLA Class II and Autoimmune
Diabetes Pp.1-15
F.
Susan Wong and Li Wen
Recent Advances on α-Synuclein
Cell Biology: Functions and Dysfunctions Pp.17-24
C.
Alves da Costa
The Posttranslational Phase of Gene
Expression: New Possibilities in Molecular Diagnosis Pp.25-38
J.F.
Rehfeld and J.P. Goetze
Cytokine Polymorphisms in Chronic
Inflammatory Diseases with Reference to Occupational Diseases Pp.39-48
Berran Yucesoy, Michael
L. Kashon and Michael I. Luster
Understanding the Tumor Metabolic Phenotype
in the Genomic Era Pp.49-59
M.
Stubbs, C.L. Bashford and J.R. Griffiths
Novel Approaches to Cancer Therapy Using Oncolytic Viruses Pp.61-71
S.F. Stanziale and Y. Fong
Signaling Pathways Regulating Gliomagenesis Pp.73-84
G.
Konopka and A. Bonni
Protein-Tyrosine Kinases
and Adaptor Proteins in FcεRI-Mediated Signaling
in Mast Cells Pp.85-94
Kiyonao Sada and Hirohei Yamamura
[Back to top] The Study of HLA Class II and Autoimmune
Diabetes
F.
Susan Wong and Li Wen
Many autoimmune
diseases have genetic associations with the Major Histocompatibility
Complex (MHC) class II loci. Susceptibility to Type 1 diabetes mellitus (TIDM)
is particularly associated with Human Leucocyte
Antigen (HLA) DR3, 4 and associated DQ2, 8 alleles and this is well documented
in genetic association studies. These molecules play an important role in
presentation of peptide antigens after intracellular processing to CD4 T
lymphocytes. During the last decade, a number of approaches have been used to
elucidate the molecular basis for the association of particular alleles with
susceptibility to or protection from TIDM. These studies have focused on
investigating the structure of the antigen presenting molecules, together with
their peptides. Through binding studies, peptide elution, molecular modelling and crystallization of the peptide MHC complex,
it has been possible to define the peptide binding regions and examine the
stability of binding of peptides from putative autoantigens.
This knowledge has also facilitated the development of reagents such as multimeric MHC-peptide complexes that will help to track
the low frequency, potentially pathogenic antigen specific cells. Recently, HLA
transgenic mice have been generated and used to study T cell epitopes. In addition, although it is clear that the
presence of HLA molecules alone does not by itself cause disease, these
transgenic mice will develop diabetes when there is an islet
“insult”, even if the islet “insult” is, itself, not
sufficient to precipitate disease in the absence of the HLA class II transgene. These mice will allow further study of the role
of these HLA molecules in vivo. We now have a much greater general
understanding of the possible reasons why particular molecules may encode
susceptibility to or protection from disease. All these studies will provide
information to ultimately define a rational basis for the development of
targeted immunotherapy.
[Back to top] Recent Advances on α-Synuclein
Cell Biology: Functions and Dysfunctions
C.
Alves da Costa
α.synuclein is a recently discovered protein that was
first identified as the major non amyloid component
of senile plaques, the cerebral lesion likely responsible for Alzheimer’s
disease. The role of α-synuclein in another
brain disease namely Parkinson’s disease, has been more deeply
documented. It appears that α-synuclein fills up
the intracytoplasmic inclusions called Lewy bodies that likely contribute to the etiology of
Parkinson’s disease. Furthermore, rare familial forms of
Parkinson’s disease have been shown to be linked to autosomal
dominant mutations of α-synucleins. Is α-synuclein a bridge between Alzheimer’s and
Parkinson’s diseases? Could it be seen as a common denominator for these
two neurodegenerative diseases? These issues could be better addressed by
further delineating the physiological function of α-synuclein
and, as a corollary, the dysfunction taking place along with the diseases.
Here, I will review the recent advances concerning the physiology of α-synuclein and will particularly focus on the post-traductional events leading to drastic biophysical
transformations. I will describe recent works suggesting that these
modifications directly modulate the normal function of α-synuclein, likely accounting for the dysfunction associated
with Parkinson’s disease and perhaps contributing to Alzheimer’s
pathology.
[Back to top] The Posttranslational Phase of Gene
Expression: New Possibilities in Molecular Diagnosis
J.F.
Rehfeld and J.P. Goetze
Proteins in
general and secretory proteins in particular undergo
posttranslational processes before they reach the structure in which they can
fulfill their functional purpose. The protein precursor may undergo a wide
variety of proteolytic cleavages, N- and C-terminal
trimmings and amino acid derivatizations in cells
that express the protein. Occasionally, the same precursor is differently
processed in different cell types and, in addition, diseased cells may process
a given precursor abnormally. For instance, the translational process is often
either increased or decreased in diseased cells, which render the ensuing
modifications of the precursor incomplete. As a result, a variable mixture of
precursors and processing-intermediates accumulates. Measurement of a single
protein or peptide component of the posttranslational processing cascade may
not facilitate the diagnosis of a disease, because the pattern of precursors
and processing products vary individually among patients.
In order to
exploit disturbed posttranslational processing for diagnostic use, and –
at the same time – provide an accurate measure of the translational
product, a simple analytical principle named “processing-independent
analysis” (PIA) has been designed. PIA-methods quantitate
the total mRNA product irrespective of the degree of precursor processing.
PIA-methods have recently been developed for a number of prohormones
and neuroendocrine proteins, and their diagnostic
potential appears promising in early diagnosis of tumors and cardiovascular
diseases.
The present review
describes posttranslational processing patterns for some neuroendocrine
proteins. Second, PIA-measurements of precursor-products are mentioned with
indication of problems and pitfalls. Finally, PIA-results obtained in diagnosis
of neoplastic and cardiovascular diseases are
highlighted. But first general aspects of the posttranslational processing are
reviewed as a necessary basis for the understanding of the new diagnostic
possibilities.
[Back to top] Cytokine Polymorphisms in Chronic
Inflammatory Diseases with Reference to Occupational Diseases
Berran Yucesoy, Michael
L. Kashon and Michael I. Luster
Genes which encode
inflammatory cytokines are subject to polymorphisms in their regulatory regions
that may effect both the level and ratio of cytokines produced in response to
exogenous stimuli. These variant alleles are observed in a large percent of the
population and are often associated with increased or decreased susceptibility
or severity (modifiers) to infectious, immune or inflammatory diseases.
Environmental factors can also play either a direct (i.e., causative factor) or
indirect (modifying factor) role in these diseases. Thus, it would follow that
gene-environment interactions would effect the expression and/or progression of
the disease. In the present review, the concept that some of the common allelic
variants found in cytokine genes represent modifying factors in chronic
inflammatory diseases associated with occupational exposure is discussed.
[Back to top] Understanding the Tumor Metabolic Phenotype
in the Genomic Era
M. Stubbs, C.L. Bashford and J.R. Griffiths
Now, at the
beginning of a new century, 80 years after Warburg’s Nobel prize winning
discoveries, we are beginning to make sense of the underlying causes of the
well known metabolic phenotype of tumor cells. Building on decades of research
to understand the interrelationships between respiration and glycolysis in cancer, the tumor metabolic phenotype can now
begin to be understood in a genomic context. With the discovery of hypoxia
inducible factor-1 (HIF-1), which is widely overexpressed
across a broad range of cancers, modern molecular tools have allowed us to put
together the pattern of events that might explain the metabolic differences
between tumor and normal cells. HIF-1 controls cellular and systemic responses
to oxygen availability and coordinates upregulation
of genes involved in many pathways concerned with tumour
growth and metabolism including angiogenesis, glucose and energy metabolism,
cellular proliferation, differentiation and viability, apoptosis, pH regulation
and matrix metabolism. These findings begin to explain how glucose uptake and glycolysis could be up-regulated in cancer cells (through
binding to a core DNA recognition sequence) in a co-ordinated
and constitutive fashion that may also allow us to elucidate new targets for
tumor therapy.
[Back to top] Novel Approaches to Cancer Therapy Using Oncolytic Viruses
S.F.
Stanziale and Y. Fong
The goal of oncolytic therapy is to exploit the innate ability of
viruses to infect tumor cells, replicate in tumor cells, and produce selective oncolysis while sparing normal cells. Although the concept
that viruses can be oncolytic is not new, it is only
in the last three decades that efforts have been directed at genetically
mutating viruses to specifically target characteristics of cancer cells.
Several viruses have the potential to infect, replicate and lyse
tumor cells, each taking advantage of different host cancer cell biology. This
review will focus on the major viruses under current investigation for oncolytic therapy, the mechanism by which they specifically
eradicate tumors, and the clinical strategies currently under investigation.
[Back to top] Signaling Pathways Regulating Gliomagenesis
G.
Konopka and A. Bonni
The astrocytomas represent the most common primary tumors of
the brain. Despite efforts to improve the treatment of astrocytomas,
these tumors and in particular the high-grade astrocytoma
termed glioblastoma multiforme
still carry a poor prognosis. In recent years, there has been an intensive
effort to gain an understanding of the cellular and molecular mechanisms that
contribute to the pathogenesis of astrocytomas as a
first step toward the development of better treatments for these devastating
tumors. Here, we will review our current understanding of the signaling
pathways that underlie glial transformation. Studies
of astrocytomas have led to the identification of two
major groups of signaling proteins whose abnormalities contribute to gliomagenesis: the cell cycle pathways and the growth
factor-regulated signaling pathways. Among the cell cycle proteins, the
p16-cdk4-pRb and ARF-MDM2-p53 cell cycle arrest pathways play a prominent role
in glial transformation. In addition, deregulation of
polypeptide growth factors acting via receptor tyrosine kinases
(RTKs) and of intracellular signals, including the
lipid phosphatase PTEN, that regulate cellular
responses to RTKs plays a critical role in gliomagenesis. In addition to the identification of the
signaling proteins targeted in glial transformation,
the cell-of-origin of astrocytomas has been
investigated. Genetic modeling of astrocytomas in mice
suggests that neuroepithelial precursor cells
represent preferred cellular substrates of gliomas or
that either astrocytes or precursor cells constitute
potential cells-of-origin of astrocytomas. During
normal brain development, neuroepithelial precursor
cells, including neural stem cells, differentiate into astrocytes.
As the mechanisms that control gliogenesis during
normal brain development become better understood, it will be important to
determine if deregulation of these mechanisms might contribute to the
pathogenesis of astrocytomas. The elucidation of the
molecular underpinnings of astrocytomas holds the
promise of improved treatment options for patients with these devastating brain
tumors.
[Back to top] Protein-Tyrosine Kinases
and Adaptor Proteins in FcεRI-Mediated Signaling
in Mast Cells
Kiyonao Sada and Hirohei Yamamura
Mast cells
function as the initiator of the allergic reaction and play a role in the
innate immune system. Aggregation of the high affinity IgE
receptor (FcεRI) on mast cells triggers degranulation with the release of chemical mediators such
as histamine, production of cytokines and leukotrienes.
FcεRI signals by activating proximal
non-receptor type of protein-tyrosine kinases, Lyn, Syk, Btk and Fyn.
Activated tyrosine kinases then phosphorylate
their specific substrates which include other enzymes and adaptor proteins and
assemble these cytoplasmic signaling molecules for
cellular activation. The adaptor proteins have multiple domains that allow binding
to effector molecules and therefore act as positive
or negative regulators controlling FcεRI
signaling. Deletion of the adaptor proteins such as LAT, SLP-76 or Gab2
resulted in decreased FcεRI-mediated
anaphylactic reaction in vivo. Functional analysis of adaptor proteins has
raised the possibility that they may be new targets for the discovery of
anti-allergic drugs.