Neurotensin (NT) is a gut peptide that plays an important role in gastrointestinal secretion, motility, and growth as well as the proliferation of NT receptor-positive cancers. Protein kinase D (PKD) family members (PKD1, 2, and 3) have been identified as important regulators of secretory transport at the trans-Golgi network. Previously, we showed that PKD1 contributes to stimulated NT secretion; however, the mechanisms are not entirely clear. Here, we show that Kidins220, which is a substrate of PKD proteins in neuroendocrine cells, is localized in the ends of the processes of BON cells, similar to the expression pattern of NT vesicles, and translocates to the membrane and large vesicle-like structures formed in response to phorbol 12-myristate 13-acetate treatment. The short hairpin RNA targeting Kidins220 inhibits NT secretion in parental BON cells or BON cells stably expressing the gastrin-releasing peptide receptor treated with either phorbol 12-myristate 13-acetate or bombesin, respectively. Furthermore, we demonstrate that endogenous PKD1, PKD2, and Kidins220 co-exist with NT-containing vesicles. Overexpression of the kinase-dead PKD1 abrogates Kidins220 expression and NT vesicle formation. Our data establish a physiological link between the PKD/Kidins220 pathway and NT-containing vesicles and suggest the role of this pathway in the regulation of hormone secretion. Because NT is an important gut hormone that affects secretion, inflammation, and both normal and tumor cell growth, our findings identify a novel signaling pathway that may be amenable to drug targeting for clinical applications.The peptide neurotensin (NT), 2 identified and characterized by Carraway and Leeman (1) from bovine hypothalamus, is produced in the brain and in enteroendocrine cells localized predominantly in the jejunum and ileum. The gastrointestinal effects of NT include facilitation of fatty acid translocation from the intestinal lumen, regulation of gut motility, and stimulation of the growth of normal gut mucosa as well as other tissues such as the adrenal gland, hepatocytes, and fibroblasts (2, 3). NT also stimulates growth of certain pancreatic, colonic, and prostatic cancers bearing NT receptors (2, 3), and recently a novel role of NT as a proinflammatory peptide has been demonstrated in the gut (4, 5). Together, these studies identify NT as an important intestinal hormone in normal physiologic functions and, furthermore, as a potential mediator of pathologic effects such as tumor growth and inflammation.Previously, we established and characterized a novel endocrine cell line, BON, derived from a human pancreatic carcinoid tumor (6). BON cells synthesize and secrete NT peptide and process the NT peptide in a manner analogous to that of enteroendocrine cells in the small bowel, thus serving as a useful model for enteroendocrine cell secretion (6). Also, BON cells have been instrumental in delineating signaling molecules that contribute to the stimulated secretion of hormones and amines from carcinoid tumors (7). Focusing on t...