The generation of biologically active polypeptide hormones by neuroendocrine cells entails a complex series of biosynthetic, maturational, and transport events. One of the most crucial early steps is proteolytic processing of the large precursor polypeptide by subtilisin-like proteolytic enzymes, the prohormone convertases (PCs). Many critical questions regarding the action of the PCs remain to be answered; in particular, the mechanisms which regulate the activity of the PCs are poorly understood. We and others have recently shown that the neuroendocrine protein 7B2 represents a binding partner for PC2 and exerts a profound influence on its biosynthesis. The carboxyl terminal peptide of this protein (7B2 CT peptide) is a potent inhibitor of PC2 and of proPC2 activation, while the amino-terminal portion of this protein (21 kDa 7B2) paradoxically facilitates the intracellular transport and the activation of proPC2 to mature PC2. Major goals of this proposal are to elucidate both the mechanism for termination of inhibition of the CT peptide as well as the mechanism by which the 21 kDa protein acts to promote proPC2 activation.
Specific aims i nclude the following: 1) to use antisense and metabolic labelling experiments to precisely define the cellular roles of 7B2 in the maturation of proPC2, and to provide structure-function relationships for the interaction of these two molecules; and 2) to use purified recombinant molecules in in vitro binding experiments to determine the affinities and optimum binding conditions of the various forms of 7B2 and PC2 for each other. We will also test the hypothesis that 7B2 is required for folding and/or during proPC2 activation. Taken together, the experiments described in this proposal should provide significant information on the cell biology and biochemistry of the interaction of proPC2/PC2 with its regulatory protein, 7B2. The long-term goal of these experiments is to understand key regulatory mechanisms in the production of bioactive peptide hormones. Ultimately this understanding may provide new avenues for the therapeutic modulation of peptide hormone levels.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK049703-05
Application #
6176486
Study Section
Endocrinology Study Section (END)
Program Officer
Haft, Carol R
Project Start
1996-09-15
Project End
2002-04-15
Budget Start
2000-08-01
Budget End
2002-04-15
Support Year
5
Fiscal Year
2000
Total Cost
$169,680
Indirect Cost
Name
Louisiana State University Hsc New Orleans
Department
Biochemistry
Type
Schools of Medicine
DUNS #
782627814
City
New Orleans
State
LA
Country
United States
Zip Code
70112
Yamamoto, Hiroyuki; Ramos-Molina, Bruno; Lick, Adam N et al. (2016) Posttranslational processing of FGF23 in osteocytes during the osteoblast to osteocyte transition. Bone 84:120-130
Ramos-Molina, Bruno; Lindberg, Iris (2015) Phosphorylation and Alternative Splicing of 7B2 Reduce Prohormone Convertase 2 Activation. Mol Endocrinol 29:756-64
Lindberg, Iris; Pang, Hong Weng; Stains, Joseph P et al. (2015) FGF23 is endogenously phosphorylated in bone cells. J Bone Miner Res 30:449-54
Liew, Chong Wee; Assmann, Anke; Templin, Andrew T et al. (2014) Insulin regulates carboxypeptidase E by modulating translation initiation scaffolding protein eIF4G1 in pancreatic ? cells. Proc Natl Acad Sci U S A 111:E2319-28
Hoshino, Akina; Helwig, Michael; Rezaei, Sina et al. (2014) A novel function for proSAAS as an amyloid anti-aggregant in Alzheimer's disease. J Neurochem 128:419-30
Yuan, Baozhi; Feng, Jian Q; Bowman, Stephen et al. (2013) Hexa-D-arginine treatment increases 7B2•PC2 activity in hyp-mouse osteoblasts and rescues the HYP phenotype. J Bone Miner Res 28:56-72
Peinado, Juan R; Sami, Furqan; Rajpurohit, Nina et al. (2013) Blockade of islet amyloid polypeptide fibrillation and cytotoxicity by the secretory chaperones 7B2 and proSAAS. FEBS Lett 587:3406-11
Helwig, Michael; Hoshino, Akina; Berridge, Casey et al. (2013) The neuroendocrine protein 7B2 suppresses the aggregation of neurodegenerative disease-related proteins. J Biol Chem 288:1114-24
Dasgupta, Indrani; Sanglas, Laura; Enghild, Jan J et al. (2012) The neuroendocrine protein 7B2 is intrinsically disordered. Biochemistry 51:7456-64
Helwig, Michael; Lee, Sang-Nam; Hwang, Jae Ryoung et al. (2011) Dynamic modulation of prohormone convertase 2 (PC2)-mediated precursor processing by 7B2 protein: preferential effect on glucagon synthesis. J Biol Chem 286:42504-13

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