PRIMARY PROTEIN STRUCTURE IN AL AMYLOIDOSIS

Project: Research project

Description

Immunoglobulin amyloidosis (AL) which is characterized by extracellular
deposition of fibril complexes composed of monoclonal immunoglobulin light
chains (LC) is the most common form of systemic amyloidosis and is
generally associated with the worst prognosis. Little is known about the
pathogenic mechanisms involved in fibril formation, but two major factors
may be involved. One is the synthesis of abnormal protein structure and a
second involves defective protein degradation. This proposal seeks to test
the hypothesis that the amino acid sequence of Ig LC variable regions plays
a determining role in the pathogenesis of AL amyloid. This hypothesis is
based on preliminary data of amino acid sequences of amyloid proteins which
show unique variations. To test this hypothesis it will be necessary to
isolate and determine the primary structure of a number of amyloid proteins
and evaluate the effect of these substitutions on secondary and tertiary
structure. Amyloid fibrils or their precursors will be isolated by
standard methods and subjected to complete amino acid sequence analysis. An important part of these studies will be the selection of appropriate LC
proteins for structural analyses. LC proteins, which have already been
assigned to subgroups by sequence analysis, will be used to make monoclonal
antibodies that are specific for the subgroups that are of interest (e.g.
kappa I, lambda I and VI). All LC (amyloid and myeloma) proteins can then
be typed so that only those belonging to the desired subgroups will be
subjected to complete sequence analysis. In this way immunologic
techniques will be used to restrict the chemical studies to a level that
can be more easily accomplished. In addition, attempts will be made to
identify monoclonal antibodies which recognize amyloid LC but not myeloma
LC. The effects of amino acid substitutions on the structure of amyloid LC will
be investigated in several ways. 1) Secondary structure analysis using
tested prediction models will be used to search for alterations in beta
sheet and turn forming potential. 2) Association constants for LC dimers
will be determined to identify any increase or decrease in intradimer
binding. 3) Computer graphics will be used to identify new intra and
intermolecular interactions generated by the amino acid substitutions found
in the amyloid subunit proteins. Using these methods we hope to define the
mechanisms of amyloid fibril formation.
StatusFinished
Effective start/end date9/23/858/31/90

Funding

  • National Institutes of Health

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Amyloidosis
Amyloid
Amino Acid Sequence
Amyloidogenic Proteins
Amino Acid Substitution
Sequence Analysis
Immunoglobulins
Immunoglobulin Variable Region
Computer Graphics
Myeloma Proteins
Protein Sequence Analysis
Proteolysis
Proteins
Monoclonal Antibodies

ASJC

  • Medicine(all)