Search PubMed⌕ Search

Biomedical subjects

T J Martin

Publications and source records attributed to T J Martin.

At least 109 records · Page 6Linked to original sources
PubMed1997

Parathyroid hormone-related protein and hypercalcemia.

The discovery of parathyroid hormone-related protein (PTH-rP) arose from interest in the mechanisms by which certain cancers cause hypercalcemia without necessarily metastasizing to bone. The humoral hypercalcemia of malignancy (HHM) had for a long time been ascribed to inappropriate production of parathyroid hormone (PTH) by cancers. The amino-terminal portions of PTH-rP and PTH have essentially identical actions through a common receptor for PTH/PTH-rP: to elevate plasma calcium by promoting bone resorption and decreasing calcium excretion. Assays for plasma PTH-rP fail to detect protein convincingly in normal plasma, but measurable levels have been found in up to 100% of patients with HHM, in 75% of patients with breast carcinoma metastatic to bone, and in some hypercalcemic patients with miscellaneous cancers. Whereas PTH-rP clearly functions as a hormone in those cancers in which it is produced in excess, in normal circumstances it is produced locally in many tissues in which it is a paracrine effector. There appears to be little doubt that PTH-rP is the major mediator of hypercalcemia in patients with HHM, although it is possible that other factors (e.g., bone resorbing cytokines) also could contribute in some patients. In the case of breast carcinoma, another possible role arises for PTH-rP. The high incidence of PTH-rP production by primary breast carcinomas, elevated plasma levels in 60% of those with hypercalcemia and lytic metastases, and higher incidence of PTH-rP production in skeletal versus those with nonskeletal metastases have led to the hypothesis that PTH-rP might contribute to breast carcinoma growth in bone. Experimental evidence currently is available to support this hypothesis. The discovery of PTH-rP has contributed greatly to current understanding of the skeletal complications of cancer.

Animals↗
PubMed1997

Alteration of local cerebral glucose utilization following intravenous administration of heroin in Fischer 344 rats.

The 2-deoxyglucose method was used to study the effects of acute administration of small intravenous doses of heroin on rates of glucose utilization in rat brain to identify small brain regions that may be involved in the acute behavioral effects of heroin. In contrast to previous studies which have used relatively large doses, the doses of heroin used in this study have been shown to be self-administered [Martin, T.J., Dworkin, S.I. and Smith, J.E., Alkylation of mu-opioid receptors by beta-funaltrexamine in vivo: comparison of the effects on in situ binding and heroin self-administration in rats., J. Pharmacol. Exp. Ther., 272 (1995) 1135-1140.]. Administration of 18 microg/kg of heroin resulted in higher rates of glucose utilization in the medial olfactory tubercle, anterior nucleus accumbens and dorsolateral caudate while having no other effects on limbic structures compared to saline-treated animals. Conversely, the rate of glucose utilization was lower than control in the habenula, dorsal raphe, and central gray following adminstration of 18 microg/kg of heroin. Administration of two higher doses (60 and 100 microg/kg) resulted in lower rates of glucose utilization in the thalamus, habenula, inferior colliculus, dorsal raphe and central gray compared to saline. The higher rates of glucose utilization in the limbic areas were specific for the lowest dose of heroin, whereas the effect of lowering the rate of glucose utilization compared to control in the thalamus and inferior colliculus were an increasing function of dose. In the habenula and dorsal raphe, however, the dose-effect function was inverted. These data indicate that the alterations of glucose utilization in rat brain by heroin are site-specific and the systems involved as well as the nature of the alteration differs for individual doses of heroin.

Analgesics, Opioid↗
PubMed1997

Potent reinforcing effects of dihydroetorphine in rats.

Dihydroetorphine is a novel opioid that is an extremely potent analgesic in rodents. The reinforcing potency was determined in rats trained to self-administer heroin and compared to those of fentanyl, heroin, 6-acetylmorphine and morphine for assessment of the abuse potential of dihydroetorphine using a procedure that determines the dose-effect curve in individual sessions. Dihydroetorphine produced a bimodal dose-effect curve similar to that of other opioids. Potency ratios were determined with morphine for the ascending and descending limbs of the dose-effect curve, as well as the dose that yielded maximal response rate. Fentanyl, heroin and 6-acetylmorphine were approximately 100, 8 and 2 times more potent than morphine in maintaining self-administration, respectively. Dihydroetorphine was roughly 1500 to 3000 times more potent than morphine, however, depending upon the limb of the dose-effect curve used for comparison. These potency ratios of dihydroetorphine to morphine were somewhat less than has been reported for analgesia assays, and therefore this compound may have some clinical advantages over other opioids. However, these studies indicate significant abuse liability for dihydroetorphine given its potency in maintaining self-administration in these animals.

Analgesics, Opioid↗
PubMed1997

Interleukin-18 (interferon-gamma-inducing factor) is produced by osteoblasts and acts via granulocyte/macrophage colony-stimulating factor and not via interferon-gamma to inhibit osteoclast formation.

We have established by differential display polymerase chain reaction of mRNA that interleukin (IL)-18 is expressed by osteoblastic stromal cells. The stromal cell populations used for comparison differed in their ability to promote osteoclast-like multinucleated cell (OCL) formation. mRNA for IL-18 was found to be expressed in greater abundance in lines that were unable to support OCL formation than in supportive cells. Recombinant IL-18 was found to inhibit OCL formation in cocultures of osteoblasts and hemopoietic cells of spleen or bone marrow origin. IL-18 inhibited OCL formation in the presence of osteoclastogenic agents including 1alpha,25-dihydroxyvitamin D3, prostaglandin E2, parathyroid hormone, IL-1, and IL-11. The inhibitory effect of IL-18 was limited to the early phase of the cocultures, which coincides with proliferation of hemopoietic precursors. IL-18 has been reported to induce interferon-gamma (IFN-gamma) and granulocyte/macrophage colony-stimulating factor (GM-CSF) production in T cells, and both agents also inhibit OCL formation in vitro. Neutralizing antibodies to GM-CSF were able to rescue IL-18 inhibition of OCL formation, whereas neutralizing antibodies to IFN-gamma did not. In cocultures with osteoblasts and spleen cells from IFN-gamma receptor type II-deficient mice, IL-18 was found to inhibit OCL formation, indicating that IL-18 acted independently of IFN-gamma production: IFN-gamma had no effect in these cocultures. Additionally, in cocultures in which spleen cells were derived from receptor-deficient mice and osteoblasts were from wild-type mice and vice versa, we identified that the target cells for IFN-gamma inhibition of OCL formation were the hemopoietic cells. The work provides evidence that IL-18 is expressed by osteoblasts and inhibits OCL formation via GM-CSF production and not via IFN-gamma production.

Animals↗
PubMed1997

PTHrP and cell division: expression and localization of PTHrP in a keratinocyte cell line (HaCaT) during the cell cycle.

Parathyroid hormone-related protein (PTHrP) is highly expressed in normal skin keratinocytes, and its involvement in growth and differentiation processes in these cells has been implicated by several lines of evidence which include the use of antisense PTHrP (Kaiser et al., 1994, Mol. Endocrinol., 8:139-147). In this study, we have investigated whether PTHrP expression and its subcellular localization is linked to cell cycle progression in a human keratinocyte cell line (HaCat), which constitutively expresses and secretes PTHrP. PTHrP mRNA and immunoreactive PTHrP were assessed in asynchronous dividing cells and in cells blocked at G1 or G2 + M phases of the cell cycle using several different protocols. The response of PTHrP mRNA expression was examined following readdition of serum in the continued presence of cycle blockers, and after release from cell cycle block, or from cell synchronization by serum deprivation. PTHrP expression was greatest in actively dividing cells when cells were in S and G2 + M phases of the cell cycle and were lowest in quiescent G1 cells. Most notable were the high levels of PTHrP mRNA and protein in cells at G2 + M phase of the cell cycle at division. Furthermore, PTHrP was localized to the nucleolus in quiescent cells, but redistributed to the cytoplasm when cells were actively dividing. Taken together, these results support a role for PTHrP in cell division in keratinocytes. In asynchronously growing cells, PTHrP expression fell as cells became confluent at a time when cell growth is inhibited and cells begin to differentiate. Mitogen stimulation of HaCaT cells resulted in a rapid increase in PTHrP mRNA expression, but was dependent upon cells being in the G1 phase of the cell cycle. Cells blocked in G1 responded to mitogen both in the continued presence of aphidicolin or when released from block. Cells blocked at G2 + M with colcemid expressed high levels of PTHrP mRNA and protein, and PTHrP mRNA did not respond further to mitogen in the continued presence of blocker. However, in cells released from block at G2 + M by addition of serum, an increase in PTHrP expression was seen coincident with the progression of cells into G1. In contrast, in a squamous cancer cell line (COLO16), basal PTHrP expression was high and was not altered during the cell cycle or by cell cycle block, consistent with association of its dysregulated expression in malignant cells. The results of this study suggest that PTHrP may have two roles in the cell cycle; one in G1 in response to mitogen, and a second at cell division when its expression is high and it is relocated from the nucleolus to the cytoplasm.

Aphidicolin↗
PubMed1997

Effects of intracerebroventricular administration of beta-funaltrexamine on DAMGO-stimulated [35S]GTP-gamma-S binding in rat brain sections.

Intracerebroventricular administration of beta-funaltrexamine (beta-FNA) reduces the density of mu opioid receptors as measured by in situ autoradiography by 40-50% throughout the brain, with little regional variation [Martin et al. (1993) J. Pharmacol. Exp. Ther. 267:506-514] Recently an assay has been developed to study opioid stimulation of [35S]GTP-gamma-S binding autoradiographically in situ using slide-mounted brain sections [Sim et al. (1995) Proc. Natl. Acad. Sci. U.S.A. 92:7242-7246]. The present study was undertaken to determine the effect of mu opioid receptor alkylation on G protein activation by the mu opioid agonist DAMGO. Animals were injected intracerebroventricularly with 40 nmol of beta-FNA or saline and sacrificed 24 hours later. DAMGO stimulated [35S]GTP-gamma-S binding with an anatomical specificity consistent with the localization of mu opioid receptors. The percent stimulation by DAMGO ranged from approximately 50 to 100% in the regions studied. beta-FNA significantly decreased G protein activation by DAMGO in regions that are consistent with its reported long-lasting and insurmountable antagonism of the antinociceptive (medial thalamus, central gray) and reinforcing (nucleus accumbens) effects of mu opioid agonists [Adams et al. (1990) J. Pharmacol. Exp. Ther. 255:1027-1032; Martin et al. (1995) J. Pharmacol. Exp. Ther. 272:1135-1140]. However, the effects of beta-FNA were not equal in all brain regions. This may indicate regional differences in the coupling efficiency of mu opioid receptors with G proteins, or in the effects of beta-FNA on mu opioid receptor binding or on mu opioid receptor-stimulated G protein activity.

Animals↗
PubMed1997

Vascular effects of PTHrP (1-34) and PTH (1-34) in the human fetal-placental circulation.

The aim of this study was to examine the vasodilatory effects of parathyroid hormone-related protein (PTHrP) (1-34) and parathyroid hormone (PTH) (1-34) on the human fetal-placental circulation utilising an in vitro placental perfusion model. In all experiments, the vasculature of an isolated human placental cotyledon was pre-constricted with the thromboxane A2 mimetic U46619. A simple dose of PTHrP (1-34) or PTH (1-34) (1.7-300 nM) was then infused into the fetal-placental circulation of the cotyledon. In other experiments, cotyledons were repeatedly infused with PTHrP (1-34) or PTH (1-34) (51.3 nM). Vasodilatory responses were significantly reduced in response to repeated exposure to PTHrP (1-34) (P < 0.001), indicating that this peptide desensitizes the fetal-placental vasculature. PTHrP (1-34) and PTH (1-34) equipotently stimulated a significant vasodilation of the fetal-placental circulation (P < 0.0001). The PTHrP receptor antagonist [Asn10, Leu 11]PTHrP (7-34) (102 nM) was infused in U46619-constricted placentae in the presence and absence of PTHrP (1-34) (10.2 nM). The PTHrP antagonist alone had no significant effect in the fetal-placental circulation. The antagonist significantly attenuated the response to PTHrP (1-34) (P < 0.015). Based on the data obtained in this study it is suggested that locally produced PTHrP (1-34) may be involved in the regulation of normal human fetal-placental vascular tone in autocrine and/or paracrine fashion.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1997

Nonenzymatic glycation of type I collagen modifies interaction with UMR 201-10B preosteoblastic cells.

Advanced glycation endproduct (AGE), whose formation is accelerated on long lived extracellular matrix proteins in diabetes, is implicated in diabetic complications in various tissues. Type I collagen is the predominant matrix protein of bone and plays an important role in bone cell-matrix interactions. We have previously reported the accelerated accumulation of AGE collagen in bone tissue in diabetes mellitus (DM), in which reduced bone mineral density was observed. In addition, when cultures of mature primary rat osteoblasts were plated onto an in vitro AGE-modified collagen substrate, they showed altered cell functions, in terms of alkaline phosphatase (ALP) activity, osteocalcin secretion, and nodule formation (J Bone Miner Res 11:931-937; 1996). To determine whether AGE collagen might also affect differentiation of preosteoblasts, we compared the effects of plating the preosteoblastic UMR 201-10B cell line onto AGE-modified collagen with plating onto unmodified collagen. The latter had been shown previously to promote differentiation of UMR 201 cells. We have also explored whether these effects might be partly mediated by the transforming growth factor beta (TGF-beta) receptor. Growth of UMR 201-10B cells on a type I collagen substrate significantly inhibited cell growth and retinoic acid (RA)-induced upregulation of ALP activity, compared to cells on plastic. These inhibitory effects were reduced by prior glycation of collagen, in a dose-dependent manner with respect to AGE content. Unmodified collagen stimulated production of osteopontin mRNA, which was reduced by AGE modification to levels attained in cells on plastic. Growth on control collagen inhibited TGF-beta type II receptor binding in 10B cells, while this inhibition was reduced by AGE modification. These data suggest that glycation of collagen interferes with specific interaction(s) between UMR 201-10B cells and collagen. Based on our previous results in UMR 201 cells, these results would be compatible with the notion that glycated collagen has reduced ability to promote differentiation of preosteoblasts to mature osteoblasts. These data further suggest that collagen-mediated events in these cells may be at least in part mediated by regulation of the TGF-beta receptor expression.

Alkaline Phosphatase↗
PubMed1997

Temporal expression of PTHrP during endochondral bone formation in mouse and intramembranous bone formation in an in vivo rabbit model.

Expression of parathyroid hormone-related protein (PTHrP) messenger RNA (mRNA) and protein was investigated throughout the developmental progression of endochondral bone formation in mouse and intramembranous bone formation in an in vivo model in rabbit, using in situ hybridization and immunohistochemistry. Endochondral bone formation was investigated in a developing embryo, newborn, and adult mouse. In fetal long bones through to newborn (day 7), PTHrP mRNA and protein were consistently expressed in chondrocytes within the proliferative, transitional, and hypertrophic zones. In addition, high levels of PTHrP were also detected in osteoblasts on the surface of trabecular bone surfaces. Similarly, at the adult stage (week 7), PTHrP mRNA and protein were consistently expressed in chondrocytes at epiphyseal ends of the subarticular cartilage, within cortical periosteum, as well as in osteoblasts located at the metaphyseal trabecular bone surfaces. Using an in vivo intramembranous bone formation model in rabbits, expression of PTHrP mRNA and protein was demonstrated in preosteoblasts prior to trabecular bone formation (1-week bone harvest). As bone formed (2-, 3-, and 4-week bone tissue harvests), PTHrP mRNA and protein were highly expressed in actively synthesizing osteoblasts and in those osteocytes embedded within the superficial layers of the bone matrix. Lining osteoblasts and osteocytes buried deeply in the bone matrix displayed weak or no signal for PTHrP. The pattern of spatial and temporal expression of PTHrP demonstrated in cartilage cells and osteoblasts in the two systems suggests an important role of PTHrP in both endochondral and intramembranous bone formation.

Animals↗
PubMed1997

Parathyroid hormone-related protein in tissues of the emerging frog (Rana temporaria): immunohistochemistry and in situ hybridisation.

Using antiserum to human parathyroid hormone-related protein (1-16) [PTHrP(1-16)] we have examined tissues of the common frog (Rana temporaria) for the presence of immunoreactive PTHrP (irPTHrP) at the stage of emergence from water to land. irPTHrP was detected in dorsal and ventral stratum granulosum of the skin, in the developing ovary, striated muscle and the choroid plexus epithelium of the brain as well as in the olfactory gland epithelium and olfactory lobe neurons of the brain. In the pituitary and hypothalamus irPTHrP protein could be demonstrated in the median eminence, infundibular stem and principally in the neural lobe and pars distalis of the pituitary with weak reaction in the pars intermedia. In situ hybridisation of the same tissues with an oligonucleotide probe to chicken PTHrP 55-65 clearly showed the presence of mRNA for PTHrP-like molecule in all the tissues containing irPTHrP. There was a major inconsistency in the pituitary in that the highest level of gene expression, assessed by in situ hybridisation, was found in the pars intermedia with only very low expression in the pars distalis and neural lobe and undetectable levels in the infundibular stem and median eminence. These observations suggest that tissues of the frog synthesise a PTHrP-like molecule but that in the pituitary the pars intermedia cells may export the protein to cells in other regions of the pituitary and hypothalamus.

Animals↗
PubMed1997

Receptors of calciotropic hormones.

The recent cloning of receptors for calcitonin (CT) and parathyroid hormone (PTH)/parathyroid hormone-related peptide (PTHrP) has enabled very rapid progress in understanding the molecular and cell biology of these receptors. In particular, much has been learnt about the tissue distribution of these receptors, as well as their mode of interaction with ligands, signal transduction and regulation of expression. The conventional view of these hormone-receptors systems as "calciotropic" has been broadened by recent work showing important developmental roles. Isoforms of the CT receptor (CTR), with interesting functional differences, have been identified and a new form of the PTH receptor, highly specific for PTH, has been cloned. Investigation of the homologous regulation of the CTR in osteoclasts by CT treatment of mouse marrow cultures, has shown that continuous exposure to CT results in formation of resorption competent, CTR-deficient osteoclasts. Treatment of mature osteoclasts causes a rapid and prolonged decrease in CTR mRNA levels, reflected in a loss of cell surface CTR. Since these cells regain resorption competence, the data support the concept that the clinical phenomenon of "escape" from the hypocalcemic action of CT results from a loss of CT sensitivity by osteoclasts to the hormone.

Animals↗
PubMed1997

Regulation by calcitonin and glucocorticoids of calcitonin receptor gene expression in mouse osteoclasts.

We previously studied regulation of the calcitonin (CT) receptor (CTR) by glucocorticoid (GC) and CT in cultures of mature mouse osteoclast-like cells (OCLs). The present studies were designed to examine the interaction of CT and GC in regulation of the CTR in osteoclasts and the molecular mechanisms involved. Treatment of OCLs with 10(-7) M dexamethasone (Dex) increased the CTR number in a time-dependent manner, whereas treatment with 10(-9) M salmon CT (sCT) reduced CTR number; neither treatment changed receptor affinity. Dex pretreatment somewhat antagonized the CT-induced reduction in [125I]sCT specific binding. Dex increased, and sCT pretreatment decreased, the sCT-responsive adenylate cyclase activity in parallel with the change in receptor binding. Dex treatment resulted in an increase in CTR messenger RNA (mRNA) levels, as assessed by reverse transcription-PCR, indicating that the increased CTR number was mediated by de novo CTR synthesis. This effect was specific to GCs and was not reproduced by mineralocorticoids or sex steroids. Treatment with sCT resulted in a rapid and profound reduction in CTR mRNA expression, and this reductions was somewhat delayed by Dex pretreatment. OCLs were treated with 5,6-dichloro-1 beta-D-ribofuranosyl benzimidazole to enable estimation of the mRNA decay rates in the absence of ongoing transcription. The stability of CTR mRNA was similar to the control value in Dex-treated OCLs, suggesting that the effect of Dex may be due to changes in transcriptional activity. Interestingly, transcriptional inhibition by 5,6-dichloro-1 beta-D-ribofuranosyl benzimidazole abolished the ability of CT to reduce CTR mRNA levels, suggesting that CT may act by increasing the rate of CTR mRNA decay, and that this effect requires ongoing transcription. The 3'-untranslated region of the mouse CTR mRNA contains four copies of the AUUUA motif, as well as other A/U-rich sequences, which have been shown to determine the stability of other mRNA transcripts. The stability results were consistent with the results of the nuclear transcript run-on assay, which indicated that treatment with Dex enhanced the rate of transcription, whereas CT had no effect. These results show that GC and CT influence CTR expression by distinct mechanisms and provide the basis for identification of the cellular factors involved.

Animals↗
PubMed1997

Plasminogen activator system in osteoclasts.

To determine which genes of the plasminogen activator (PA) system were expressed in osteoclasts, RNA extracted from microisolated mouse osteoclasts was used as template for reverse transcribed polymerase chain reaction (RT-PCR) with gene-specific primer pairs. Using this approach, the expression of RNAs for tissue-type plasminogen activator, urokinase-type plasminogen activator, plasminogen activator inhibitor-1, plasminogen activator inhibitor-2, protease nexin, and urokinase receptor isoform 1 (uPAR1) were detected in mouse osteoclasts. The expression of uPAR RNA in osteoclasts was confirmed by in situ hybridization with a uPAR1 probe. RNA encoding the uPAR isoform 2 was not detected in mouse osteoclasts, but a novel unspliced uPAR RNA variant was detected in these cells. The novel uPAR variant and uPAR1 RNA were also detected in mouse calvarial osteoblasts, kidney, muscle, and the mouse macrophage cell line J774A.1 by RT-PCR. The presence of RNAs for most of the components of the PA system in osteoclasts suggests that it may have a functional role in this cell type.

Animals↗
PubMed1997

Parathyroid hormone-related protein: hormone and cytokine.

While PTHrP acts as a hormone when it is produced in excess by certain cancers, and perhaps also in lactating women, the foetus, and lower vertebrates, it seems clear that PTHrP is an important paracrine regulator of several tissue-specific functions. Its roles in smooth muscle relaxation, placental calcium transport, and bone development are becoming firmly established. However, it is likely to be an important player in the control of cellular growth and differentiation, although much of our understanding of this role to date comes from indirect evidence. The next decade will be an exciting time in defining further both the hormonal and paracrine actions of PTHrP.

Animals↗
PubMed1996

The role of gp130-mediated signals in osteoclast development: regulation of interleukin 11 production by osteoblasts and distribution of its receptor in bone marrow cultures.

Interleukin (IL)-11 is a multifunctional cytokine whose role in osteoclast development has not been fully elucidated. We examined IL-11 production by primary osteoblasts and the effects of rat monoclonal anti-mouse glycoprotein 130 (gp130) antibody on osteoclast formation, using a coculture of mouse osteoblasts and bone marrow cells. IL-1, TNF alpha, PGE2, parathyroid hormone (PTH) and 1 alpha,25-dihydroxyvitamin D3 (1 alpha,25(OH)2D3) similarly induced production of IL-11 by osteoblasts, but IL-6, IL-4, and TGF beta did not. Primary osteoblasts constitutively expressed mRNAs for both IL-11 receptor (IL-11R alpha) and gp130. Osteotropic factors did not modulate IL-11R alpha mRNA at 24 h, but steady-state gp130 mRNA expression in osteoblasts was upregulated by 1 alpha,25(OH)2D3, PTH, or IL-1. In cocultures, the formation of multinucleated osteoclast-like cells (OCLs) in response to IL-11, or IL-6 together with its soluble IL-6 receptor was dose-dependently inhibited by rat monoclonal anti-mouse gp130 antibody. Furthermore, adding anti-gp130 antibody abolished OCL formation induced by IL-1, and partially inhibited OCL formation induced by PGE2, PTH, or 1 alpha,25(OH)2D3. During osteoclast formation in marrow cultures, a sequential relationship existed between the expression of calcitonin receptor mRNA and IL-11R alpha mRNA. Osteoblasts as well as OCLs expressed transcripts for IL-11R alpha, as indicated by RT-PCR analysis and in situ hybridization. These results suggest a central role of gp130-coupled cytokines, especially IL-11, in osteoclast development. Since osteoblasts and mature osteoclasts expressed IL-11R alpha mRNA, both bone-forming and bone-resorbing cells are potential targets of IL-11.

Animals↗
PubMed1996

PC8 [corrected], a new member of the convertase family.

A novel subtilisin-like protein, PC8, was identified by PCR using degenerate primers to conserved amino acid residues in the catalytic region of members of the prohormone convertase family. PC8 was predicted to be 785 residues long and was structurally related to the mammalian convertases furin, PACE4, PC1 and PC2, sharing more than 50% amino acid identity over the catalytic region with these family members. PC8 possessed the catalytically important Asp, His, Asn and Ser amino acids, the homo B domain of this family of enzymes and a C-terminal hydrophobic sequence indicative of a transmembrane domain. Structurally, PC8 is more related to furin and PACE4 than to PC1 or PC2. Like furin and PACE4, PC8 mRNA was found to be widely expressed; this is in contrast with PC1 and PC2, which have a restricted distribution. Two transcripts, of 4.5 and 3.5 kb, were detected in both human cell lines and rat tissues. Unlike furin and PACE4, both of which map to chromosome 15, PC8 maps to chromosome 11q23-11q24, suggesting that this gene may have resulted from an ancient gene duplication event from either furin or PACE4, or conversely that these genes arose from PC8.

Amino Acid Sequence↗