ROLE OF CELL SHAPE IN HORMONE PROCESSING

Extracellular matrices play a critical role in cell growth and
differentiation in part by influencing cell shape. PC 12 cells are a
clonal cell line which exhibits a dramatic change in cell shape and in the
release of dopamine when cultured on extracellular matrix. Since these
cells also produce the peptide hormones, enkephalin and vasoactive
intestinal peptide (VIP); and manifest acetylcholine and glucocorticoid
receptors, they provide an excellent model for definitive studies on the
role of cell shape in releasing and responding to chemical messengers,
i.e., hormones. Numerous functional properties relating to hormone
production and secretion will be compared in PC 12 cells which are
flattened on extracellular matrix versus rounded on plastic. These
functional properties include: dopamine secretion, storage, synthesis,
uptake, and turnover; enkephalin secretion, synthesis and storage;
vasoactive intestinal peptide secretion, synthesis and storage;
acetylcholine sensitivity and receptor binding characteristics;
glucocorticoid sensitivity and receptor binding characteristics; and
adenylate cyclase activity and sensitivity. A radioenzymatic assay is used
to measure catecholamine secretion and storage. Radioimmunoassays for
enkephalin and VIP will be used to measure secretion and storage.
Radiolabeled tyrosine and Dowex resin chromatography will be used to
determine dopamine synthesis and turnover. Radiolabeled norepinephrine
will be used in experiments examining re-uptake function. Radiolabeled
leucine or methionine in combination with immunoprecipitation of enkephalin
and VIP will be used to examine synthesis of the peptide hormones.
Radiolabeled receptor ligands will be used to characterize the
acetylcholine and glucocorticoid receptor properties in the cells which are
flattened on matrix versus rounded on plastic. During development a single
cell becomes a multicellular organism composed of many different cells with
a complexity of functions. This process involves growth, migration and
differentiation of cells. Mistakes in this process result in all forms of
birth defects and death. During differentiation various parts of the
genome are activated or repressed at critical times, but the cues for this
process are not well understood. Cells transmit and receive information to
and from their environment which must play a role in gene expression. This
information appears to involve chemical signals as well as physical
position. This project proposal abstracts from these concepts as it
focuses on the role of cell shape in hormone secretion and processing.