Expression of N-CAM polypeptides in neurons

Area of Science:

• Neuroscience
• Cell Biology
• Developmental Biology

Background:

• Neural Cell Adhesion Molecule (N-CAM) exists in three polypeptide forms (A, B, C) in rat brain.
• Cultured neurons were previously thought to express only N-CAM A and B, while glial cells express B and C.
• The increasing biosynthesis of N-CAM C during postnatal development suggested neuronal differentiation or increased glial contribution.

Purpose of the Study:

• To investigate the expression of N-CAM polypeptides in neurons.
• To determine if neurons are capable of synthesizing the N-CAM C-polypeptide.
• To clarify the cellular sources of developmentally regulated N-CAM C expression.

Main Methods:

• Biosynthetic labeling of cultured peripheral ganglia and adrenal chromaffin cells.
• Cell-free translation of microsomes from neuronal cultures.
• In vivo biosynthetic labeling of retinal ganglion neurons in rats.

Main Results:

• Cultured neurons synthesized N-CAM A, B, and C, although C production capacity was low.
• Neuronal microsomes contained messenger RNA encoding for the N-CAM C-polypeptide.
• Retinal ganglion neurons expressed N-CAM C in their natural environment in vivo.

Conclusions:

• Neurons possess the capability to synthesize the N-CAM C-polypeptide.
• Both neurons and glial cells may contribute to the developmental regulation of N-CAM C expression.
• The study revises the understanding of N-CAM expression patterns in neuronal development.