The Education Review Board: A Mechanism for Managing Potential Conflicts of Interest in Medical Education.

Concerns about the influence of industry support on medical education, research, and patient care have increased in both medical and political circles. Some academic medical centers, questioning whether industry support of medical education could be appropriate and not a conflict of interest, banned such support. In 2009, a Partners HealthCare System commission concluded that interactions with industry remained important to Partners' charitable academic mission and made recommendations to transparently manage such relationships.

Nuclear translocation of CBP/p300-interacting protein CITED1 induced by parathyroid hormone requires serine phosphorylation at position 79 in its 63-84 domain.

The transcriptional cofactor CITED1 inhibits osteoblastic differentiation and blunts the stimulation of osteoblastic differentiation by parathyroid hormone (PTH). In the MC3T3-E1 osteoblastic cell line, we found that CITED1 was located predominantly in the cytoplasm and that hPTH(1-34) increased translocation of CITED1 from the cytoplasm to the nucleus. This response to hPTH(1-34) was not observed when all 9 serine residues within the 63-84 domain of CITED1 were mutated to alanines (CITED1 9S>A) or when a single serine to alanine mutation was made at position 79 (CITED1 S(79)>A).

Activation of a non-cAMP/PKA signaling pathway downstream of the PTH/PTHrP receptor is essential for a sustained hypophosphatemic response to PTH infusion in male mice.

PTH increases urinary Pi excretion by reducing expression of two renal cotransporters [NaPi-IIa (Npt2a) and NaPi-IIc (Npt2c)]. In contrast to acute transporter regulation that is cAMP/protein kinase A dependent, long-term effects require phospholipase C (PLC) signaling by the PTH/PTHrP receptor (PPR). To determine whether the latter pathway regulates Pi through Npt2a and/or Npt2c, wild-type mice (Wt) and animals expressing a mutant PPR incapable of PLC activation (DD) were tested in the absence of one (Npt2a(-/-) or Npt2c(-/-)) or both phosphate transporters (2a/2c-dko).

Loss of wnt/β-catenin signaling causes cell fate shift of preosteoblasts from osteoblasts to adipocytes.

Wnt signaling is essential for osteogenesis and also functions as an adipogenic switch, but it is not known if interrupting wnt signaling via knockout of β-catenin from osteoblasts would cause bone marrow adiposity. Here, we determined whether postnatal deletion of β-catenin in preosteoblasts, through conditional cre expression driven by the osterix promoter, causes bone marrow adiposity. Postnatal disruption of β-catenin in the preosteoblasts led to extensive bone marrow adiposity and low bone mass in adult mice.

Targeted ablation of the PTH/PTHrP receptor in osteocytes impairs bone structure and homeostatic calcemic responses.

Parathyroid hormone (PTH) is a major physiologic regulator of calcium, phosphorous, and skeletal homeostasis. Cells of the osteoblastic lineage are key targets of PTH action in bone, and recent evidence suggests that osteocytes might be important in the anabolic effects of PTH. To understand the role of PTH signaling through the PTH/PTHrP receptors (PPR) in osteocytes and to determine the role(s) of these cells in mediating the effects of the hormone, we have generated mice in which PPR expression is specifically ablated in osteocytes.

Phospholipase C signaling via the parathyroid hormone (PTH)/PTH-related peptide receptor is essential for normal bone responses to PTH.

We have previously shown that differentiation of hypertrophic chondrocytes is delayed in mice expressing a mutated PTH/PTHrP receptor (PTHR) (called DSEL here) that stimulates adenylyl cyclase normally but fails to activate phospholipase C (PLC). To better understand the role of PLC signaling via the PTHR in skeletal and mineral homeostasis, we examined these mice fed a normal or calcium-deficient diet. On a standard diet, DSEL mice displayed a modest decrease in bone mass.

Suppression of Wnt signaling by Dkk1 attenuates PTH-mediated stromal cell response and new bone formation.

Parathyroid hormone (PTH) suppresses Dickkopf 1 (Dkk1) expression in osteoblasts. To determine whether this suppression is essential for PTH-mediated Wnt signaling and bone formation, we examined mice that overexpress Dkk1 in osteoblasts (Dkk1 mice). Dkk1 mice were osteopenic due to abnormal osteoblast and osteoclast activity.

Functional analysis of a type 1 parathyroid hormone receptor intracellular tail mutant [KRK(484-6)AAA]: effects on second messenger generation and cellular targeting.

The parathyroid hormone receptor type 1 (PTHR1) is activated by parathyroid hormone (PTH) and PTH-related protein (PTHrP) and primarily signals via intracellular pathways involving adenylyl cyclase and phospholipase C. The intracellular tail domain of the PTHR1 contributes to G protein subunit coupling that is important for second messenger signalling. In addition, the intracellular domain has a potential nuclear localization sequence (NLS) that, if functional, could point to an intracrine role for the receptor.

CBP/p300-interacting protein CITED1 modulates parathyroid hormone regulation of osteoblastic differentiation.

PTH regulates osteoblastic differentiation and activity and exerts different overall skeletal effects in vivo, depending on the schedule and dose of administration. In clonal Wt9 murine osteoblastic cells, mRNA and protein levels of CITED1 transcriptional coactivator were strongly up-regulated by human (h) PTH(1-34). Stimulation of CITED1 mRNA by PTH was transient, peaking at 4 h, concentration dependent, and blocked by actinomycin D but not cycloheximide.

Expression of PTH1R constructs in LLC-PK1 cells: protein nuclear targeting is mediated by the PTH1R NLS.

This study demonstrates that the PTH1R NLS can target a fusion protein to the nucleus, and that this is blocked by sequences downstream of the NLS. GFP fused to the NLS showed a significant increase in nuclear targeting compared to GFP alone or GFP fused to a peptide of the same length. In previous studies, we demonstrated that the type I PTH/PTHrP receptor (PTH1R) localizes to the nucleus of cells within rat liver, kidney, uterus, ovary and gut.

Contributions of parathyroid hormone (PTH)/PTH-related peptide receptor signaling pathways to the anabolic effect of PTH on bone.

PTH regulates osteoblastic function by activating PTH/PTHrP receptors (PTH1Rs), which trigger several signaling pathways in parallel, including cAMP/protein kinase A (PKA) and, via both phospholipase-C (PLC)-dependent and PLC-independent mechanisms, protein kinase C (PKC). These signaling functions have been mapped to distinct domains within PTH(1-34), but their roles in mediating the anabolic effect of intermittent PTH in vivo are unclear. We compared the anabolic effects in mice of hPTH(1-34) with those of two analogs having restricted patterns of PTH1R signaling.

Synthesis and characterization of novel biotinylated carboxyl-terminal parathyroid hormone peptides that specifically crosslink to the CPTH-receptor.

Parathyroid hormone (PTH) regulates calcium, phosphorous and skeletal homeostasis via interaction with the G protein-coupled PTH/PTHrP receptor, which is fully activated by the amino-terminal 34 amino-acid portion of the hormone. Recent evidence points to the existence of another class of receptors for PTH that recognize the carboxyl (C)-terminal region of intact PTH (1-84) (CPTHRs) and are highly expressed by osteocytes. Here we report the synthesis and characterization of two novel bifunctional CPTH ligands that include benzoylphenylalanine (Bpa) substitutions near their amino-termini and carboxyl-terminal biotin moieties, as well as a tyrosine(34) substitution to enable radioiodination.

Regulation of C-terminal and intact FGF-23 by dietary phosphate in men and women.

Unlabelled: FGF-23 is a novel regulator of phosphate metabolism. We studied the regulation of FGF-23 by dietary phosphate in 66 men and women using two assays. Dietary phosphate restriction decreased FGF-23 and loading increased FGF-23 significantly.

Role of calcium channels in carboxyl-terminal parathyroid hormone receptor signaling.

Parathyroid hormone (PTH), an 84-amino acid polypeptide, is a major systemic regulator of calcium homeostasis that activates PTH/PTHrP receptors (PTH1Rs) on target cells. Carboxyl fragments of PTH (CPTH), secreted by the parathyroids or generated by PTH proteolysis in the liver, circulate in blood at concentrations much higher than intact PTH-(1-84) but cannot activate PTH1Rs. Receptors specific for CPTH fragments (CPTHRs), distinct from PTH1Rs, are expressed by bone cells, especially osteocytes.

PTH/PTHrP receptor delays chondrocyte hypertrophy via both Runx2-dependent and -independent pathways.

The transcription factor, Runx2, promotes chondrocyte hypertrophy, whereas parathyroid hormone-related protein (PTHrP) delays this process. To examine whether PTHrP suppresses chondrocyte hypertrophy via Runx2-dependent or -independent pathways, Runx2 expression and chondrocyte differentiation were analyzed using bones from embryonic limbs of wild type and Runx2(-/-) mice. Treatment of cultured rudiments with PTH dramatically suppresses Runx2 mRNA levels in hypertrophic chondrocytes.

Parathyroid hormone activates PKC-delta and regulates osteoblastic differentiation via a PLC-independent pathway.

PTH exerts major effects upon bone by activating PTH/PTHrP receptors (PTH1Rs) expressed on osteoblasts. The PTH1R is capable of engaging multiple signaling pathways in parallel, including Gs/adenylyl cyclase (AC), Gq/phospholipase C/protein kinase C (PLC/PKC) and a distinct mechanism, involving activation of PKC via a PLC-independent pathway, that depends upon ligand determinants within the PTH(29-34) sequence. The involvement of PLC-dependent vs.

PTH receptors and apoptosis in osteocytes.

Osteocytes comprise a heterogenous population of terminally differentiated osteoblasts that direct bone remodeling in response to applied mechanical loading of bone. Increased osteocyte density accompanies the anabolic effect of PTH in vivo, whereas accelerated osteocyte death may be precipitated by estrogen deficiency or excess glucocorticoid exposure (conditions benefitted by intermittent PTH therapy) and by renal failure (where circulating intact PTH and, especially, PTH carboxylfragments are elevated). Osteocytes express type-1 PTH/ PTHrP receptors (PTH1Rs), which are fully activated by aminoterminal PTH fragments and couple to multiple signal transducers, including adenylyl cyclase and phospholipase C.

Parathyroid hormone secretion and action: evidence for discrete receptors for the carboxyl-terminal region and related biological actions of carboxyl- terminal ligands.

PTH is a major systemic regulator of the concentrations of calcium, phosphate, and active vitamin D metabolites in blood and of cellular activity in bone. Intermittently administered PTH and amino-terminal PTH peptide fragments or analogs also augment bone mass and currently are being introduced into clinical practice as therapies for osteoporosis. The amino-terminal region of PTH is known to be both necessary and sufficient for full activity at PTH/PTHrP receptors (PTH1Rs), which mediate the classical biological actions of the hormone.

Receptors specific for the carboxyl-terminal region of parathyroid hormone on bone-derived cells: determinants of ligand binding and bioactivity.

PTH comprises 84 amino acids of which the first 34 are sufficient for full activation of the classical PTH/PTHrP receptor, the type 1 PTH receptor. It is known that multiple carboxyl (C)-terminal fragments of PTH are present in the blood and that they comprise the majority of circulating PTH. C-PTH fragments, previously regarded as by-products of PTH metabolism, are directly secreted by the parathyroid glands or arise from the peripheral cleavage of the intact hormone.

Osteoblastic cells regulate the haematopoietic stem cell niche.

Stem cell fate is influenced by specialized microenvironments that remain poorly defined in mammals. To explore the possibility that haematopoietic stem cells derive regulatory information from bone, accounting for the localization of haematopoiesis in bone marrow, we assessed mice that were genetically altered to produce osteoblast-specific, activated PTH/PTHrP receptors (PPRs). Here we show that PPR-stimulated osteoblastic cells that are increased in number produce high levels of the Notch ligand jagged 1 and support an increase in the number of haematopoietic stem cells with evidence of Notch1 activation in vivo.

Cyclic adenosine monophosphate/protein kinase A mediates parathyroid hormone/parathyroid hormone-related protein receptor regulation of osteoclastogenesis and expression of RANKL and osteoprotegerin mRNAs by marrow stromal cells.

Parathyroid hormone (PTH) is a major regulator of osteoclast formation and activation, effects that are associated with reciprocal up- and down-regulation of RANKL and osteoprotegerin (OPG), respectively. The roles of specific downstream signals generated by the activated PTH/PTH-related protein (PTHrP) receptor (PTH1R), such as cyclic adenosine monophosphate/protein kinase A (cAMP/PKA) and phospholipase C/protein kinase C (PLC/PKC), in controlling RANKL and OPG expression and osteoclastogenesis remain uncertain. In MS1 conditionally transformed clonal murine marrow stromal cells, which support PTH-induced osteoclast formation from cocultured normal spleen cells, PTH(1-34) increased RANKL and macrophage colony-stimulating factor (M-CSF) mRNA expression and decreased that of OPG when present continuously for 7-20 days at 37 degrees C in the presence of dexamethasone (Dex).

The PTH/PTHrP receptor can delay chondrocyte hypertrophy in vivo without activating phospholipase C.

One G protein-coupled receptor (GPCR) can activate more than one G protein, but the physiologic importance of such activation has not been demonstrated in vivo. We have generated mice expressing exclusively a mutant form of the PTH/PTHrP receptor (DSEL) that activates adenylyl cyclase normally but not phospholipase C (PLC). DSEL mutant mice exhibit abnormalities in embryonic endochondral bone development, including delayed ossification and increased chondrocyte proliferation.

Estrogen inhibition of PTH-stimulated osteoclast formation and attachment in vitro: involvement of both PKA and PKC.

Estrogens modulate the catabolic effects of PTH on bone in vivo and in vitro. PTH-stimulated cAMP accumulation in osteoblasts is thought to be linked to increased osteoclastic activity, but the precise mechanism is still unknown. In cocultures of clonal marrow stromal cells (MS1) and normal mouse spleen cells, both 1,25-dihydroxyvitamin D3 and rat PTH (rPTH)-(1-34) can induce the formation of tartrate-resistant acid phosphatase- and calcitonin receptor-positive multinucleated osteoclast-like cells, which can attach to dentine slices and produce resorption pits.

Human PTH-(7-84) inhibits bone resorption in vitro via actions independent of the type 1 PTH/PTHrP receptor.

The linear sequence of intact mammalian PTH consists of 84 amino acids, of which only the most amino(N)-terminal portion, i.e. PTH-(1-34), is required for the classical actions of the hormone on mineral ion homeostasis mediated by the type 1 PTH/PTHrP receptor (PTH1R).