• Fallon, Robert (PI)

Project: Research project

Project Details


Receptor-mediated endocytosis (RME) is a system for the transfer into the
cell of large molecules involved in cell nutrition, activation or
mitogenesis. Of the large number of receptor systems described, e.g. LDL
receptor, epidermal growth factor, insulin receptor, transferrin receptor,
none is understood in detail at the molecular level. This research
proposal investigates this area of cell biology using as a model system the
asialoglycoprotein receptor (ASGP-R) in a human hepatoma-derived cell
line. The ASGP-R is well suited to these studies as there are purified
ligands, anti-receptor antibodies, and purified receptor protein and
fragments thereof available in the sponsor's laboratory. In addition the
basic cell biology of the receptor protein has been well characterized by
the sponsor over the last four years. Specific aims of this proposal include the study of phosphorylation of the
ASGP receptor in intact cells and in isolated plasma membranes. The
precise molecular domains of phosphate additions and a characterization of
the kinase enzymes responsible for these reactions will be investigated in
an in vitro system. Altered states of receptor phosphorylation will be
investigated using biochemical agents that perturb cell function (ligand,
phorbol esters, calcium ionophores). Preliminary data have been
accumulated suggesting changes in receptor phosphorylation under these
conditions as well as simultaneous changes in receptor phosphorylation and
RME in these cells. These studies involve binding of radioactively
labelled ligand, cell fractionation and immunological isolation of
internalized receptor, and colloidal gold immunocytoelectron microscopy. The goal of these studies is to equip the candidate with a broad range of
biochemical and morphological skills in cell biology, while investigating a
basic problem in receptor biology in a well-characterized model system.
This program will prepare the candidate for a subsequent application of
this information to the regulation of hematopoietic progenitors by growth
factor receptors. Techniques for the isolation and purification of these
cells are well developed within the candidate's division. This will
permit, when combined with the requisite biochemical tools, detailed
studies on a molecular level into the pathophysiology of bone marrow
failure syndromes, both congenital and acquired.
Effective start/end date7/1/8611/30/90


  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health


  • Medicine(all)


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