Stimulation of inositol phosphate formation in ros 17/2.8 cell membranes by guanine nucleotide, calcium, and parathyroid hormone

Abstract

In addition to stimulation of cyclic AMP, parathyroid hormone (PTH) may influence cellular events by utilizing other pathways of hormone action, such as the generation of inositol phosphates (IPs). We sought to examine this potential action of PTH by assessing the formation of inositol phosphates in PTH-sensitive ROS 17/2.8 cells. The polyphosphoinositides were labeled by growing the cells with [3H]inositol following which cell homogenates were prepared. The nonhydrolyzable guanine nucleotide, GTP gamma S, and calcium ion, alone and together, stimulated all three IPs, IP1, IP2, and IP3. IP1 formation was linear over 30 minutes but IP2 and IP3 accumulated more rapidly peaking by 5 minutes for all agonist conditions. The proportion of total P as IP3 was enhanced when the cells were grown with retinoic acid (1 microM) or when the assay was conducted at pH 4.5. In addition, the lower pH was associated with much more enzyme activity. PTH agonists, bPTH-(1-84) and bPTH-(1-34), both caused a small but significant stimulation of IP3 formation. When bPTH-(1-84), and the analog bPTH-(3-34)amide, that inhibits PTH-mediated adenylate cyclase activity were present together, there was additive stimulation of IP3 formation compared with that with either agent alone. The results demonstrate that inositol phosphate formation can be stimulated directly in a membrane preparation of ROS cells by GTP gamma S, calcium ion, and PTH and that the enzyme mediating this activity, phospholipase C, is regulated by a guanine nucleotide binding protein.

Voltage-Gated Calcium Channels in Nonexcitable Tissues

“…TRPC channel activation is downstream of phospholipase C (PLC), so G protein-coupled receptor signaling events that activate PLC are poised to open VGCCs. Of note, the parathyroid hormone that stimulates Ca 2+ influx through VGCCs in ROS 17/2.8 activates PLC (90), and ROS 17/2.8 cells have TPRC3 transcripts (91).…”

Development of craniofacial structures in transgenic mice with constitutively active PTH/PTHrP receptor

“…PTH is synthesized by the parathyroid glands and acts on kidney and bone to regulate calcium homeostasis [3][4][5]. PTH stimulates multiple intracellular signals that include cyclic adenosine monophosphate (cAMP) [6][7][8][9], inositol phosphate, and calcium [10][11][12][13][14][15], and activates both protein kinase A [16] and C [17]. PTHrP, in contrast, is synthesized in multiple tissues with specific spatial and temporal profiles and has largely paracrine functions [4,[18][19][20][21].…”

Hypercalcemia of Malignancy

“…PTHRP has also been shown to inhibit collagen synthesis in avian epiphyseal cartilage cells (Pines et al 1990). These effects of PTHRP may be mediated through its activation of protein kinase C and inositol trisphosphate second messenger systems that were observed in UMR-106 and ROS 17/28 osteoblast-like osteosarcoma cells (Babich et al 1990;Cosman et al 1989).…”

“…Although its overall structure is similar to that of other of Early studies on the structure-function of the ligand have shown that deletion of the two N-terminal amino acids of PTH or PTHRP results in dramatic loss of adenylyl cyclase-stimulating ability (Rabbani et al 1988). without adversely affecting activation of phospholipase C and phosphoinositide synthesis (Cosman et al 1989). More recently, the C-terminal truncated PTH (1-31) has been shown to activate adenylyl cyclase.…”