Laminin induces formation of neurite-like processes and potentiates prolactin secretion by GH3 rat pituitary cells.
Tumor-derived GH3 rat pituitary cell lines are widely utilized to study mechanisms of prolactin secretion and responsiveness to secretagogues. These cells served here as a model with which to study relationships between shape and function. When GH3 cells were routinely grown in serum-supplemented medium, they exhibited the polygonal phenotype of epithelial cells, with scarce secretory granules. In contrast, when seeded in a serum-free medium, they attached loosely and contained more secretory granules. In both cases, they released prolactin in a nonpolarized manner. We show in the present work that laminin extracted from Englebreth-Holm-Swarm (EHS) tumors was a potent attachment and spreading factor for GH3/B6 cells seeded in serum-free medium. Moreover, it induced the formation of neurite-like processes, which were increased in number and length by chronic treatment with a specific secretagogue, thyroliberin (TRH). These changes in cell shape were correlated with a potentiation of prolactin secretion, both basal and TRH-stimulated. Furthermore, using immunocytochemistry and electron microscopy, we revealed--at the dilated tip of processes--an accumulation not only of prolactin, but also of synaptophysin, a vesicle membrane marker, and of several organelles, such as secretory granules, smooth vesicles, dense bodies and mitochondria. The cytoplasmic processes contained long parallel bundles of microtubules and showed a strong immunoreactivity for beta 2-tubulin. In addition, we found immunocyto-chemical evidence for the presence of 200-k Da neurofilament protein in GH3/B6 cell processes as well as in neurites of cultured hypothalamic neurons. We conclude that, in GH3/B6 cells, laminin induced the differentiation of neurite-like processes, which were the site of polarized organelle transport and exhibited some neuronal markers.
Brunet-de Carvalho
N
N
Groupe de Neuroendocrinologie Cellulaire et Moléculaire, Collège de France, Paris.
Picart
R
R
Van de Moortele
S
S
Tougard
C
C
Tixier-Vidal
A
A
D000818:Animals; D001692:Biological Transport; D002448:Cell Adhesion; D002454:Cell Differentiation; D003594:Cytoplasmic Granules / Q000502:physiology / Q000648:ultrastructure; D003599:Cytoskeleton / Q000502:physiology / Q000648:ultrastructure; D007150:Immunohistochemistry; D007797:Laminin / Q000502:physiology*; D008565:Membrane Proteins / Q000502:physiology; D008854:Microscopy, Electron; D009474:Neurons / Q000166:cytology; D010903:Pituitary Gland, Anterior / Q000166:cytology*; D011388:Prolactin / Q000378:metabolism*; D051381:Rats; D016708:Synaptophysin; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D007797:Laminin; D008565:Membrane Proteins; D016708:Synaptophysin; D013973:Thyrotropin-Releasing Hormone; D011388:Prolactin