The local anesthetic properties and toxicity of saxitonin homologues for rat sciatic nerve block in vivo

BACKGROUND AND OBJECTIVES

Saxitoxin and its homologues are naturally occurring compounds that block the sodium channel with high potency. They have the potential for providing prolonged duration local anesthesia when coinjected with vasoconstrictors or conventional local anesthetics and are devoid of local neurotoxicity. Here, we compare sciatic nerve block with saxitoxin to those with neosaxitoxin, decarbamoyl saxitoxin, and tetrodotoxin (TTX), in a search for even safer compounds.

METHODS

Rats received percutaneous sciatic nerve block with toxins. The compounds were compared in terms of lethality, onset and duration of action for thermal analgesia (hot-plate testing), and motor block (weight-bearing). Data were expressed as medians with 25th and 75th percentiles, and median effective concentrations were determined.

RESULTS

The median concentrations at which analgesia of 60 minutes duration was achieved were neosaxitoxin, 34+/-2 micromol/L; saxitoxin, 58+/-3 micromol/L; TTX, 92+/-5 micromol/L; and decarbamoyl saxitoxin, 268+/-8 micromol/L. Similar trends were observed for other measures of effectiveness (block duration of 90 minutes, maximal block), and for lethality so that the therapeutic indices were similar. No toxin had a marked predominance of sensory or motor block. The potency of TTX was intermediate between those of the saxitoxins, and its therapeutic index was slightly better. No difference was observed in time to onset of nerve blockade among the toxins.

CONCLUSIONS

Substitutions on the saxitoxin nucleus result in large differences in incidence and duration of block, and toxicity. The therapeutic indices of the saxitoxins are similar; that of TTX is slightly better.

[Clinical study of metastasis of thoracic lymph node in resectable lung cancer]

OBJECTIVE

To study the metastatic pattern of thoracic lymph node in resectable lung cancer.

METHODS

From January 1992 to July 1998, the lymph nodes in hilar(N1) and mediastinal(N2) were resected based on their distribution in 160 patiens with resectable lung cancer and were examined by pathology. Number, size and colour of lymph nodes in each regions were recorded. Each lymph node was examined by routine pathology and immunohistochemistry. Quantity of metastatic lymph node was reported according to their regions.

RESULTS

99 cases(61.9%) had thoracic lymph nodes metastasis and 73 cases (45.6%) had mediastinal lymph nodes metastasis. Of those, only N1 metastasis was 16.3%, from N1 to N2 metastasis was 32.5%, only N2 metastasis was 13.1%. The metastatic frequencies in 11, 10, 7, 5 and 4 regions around the hilar or root of lung were 30.0%, 27.5%, 16.9%, 28.8% and 20.0%, respectively. Those were higher than 9, 6, 3, 2 and 1 regions far from the root of lung. The metastatic rate of lymph node in 2.0 cm or greater, 1.0 cm or greater and less than 1.0 cm was 60.7%, 15.5% and 4.3%, respectively (P < 0.001). The smallest metastatic lymph node was only 0.2 cm x 0.2 cm. Statistical analysis revealed that metastatic rate of thoracic lymph nodes was not relevant to different area, size and course of tumors.

CONCLUSIONS

The lymph nodes metastases of most cases were spreading from the near to the distant, from lower to upper, through the hilar to the mediastinal. Lymph nodes metastases occurred easier in SCLC than in NSCLC (P < 0.05). It must be depended on pathologic examination to confirm whether or not the tumor has metastasis to lymph node.

[Cytological diagnosis of Hashimoto's hyperthyroidism]

OBJECTIVE

To assess the value of thyroid fine needle biopsy (FNB) in Hashimoto's hyperthyroidism.

METHODS

FNB for was performed 58 (5 males and 53 females, aged from 13 to 66 years) of 1 031 patients who was performed clinically dignosised as having hyperthyroidism according to clinic symptoms, the results of physical and, laboratory examination, especially the increased the serum circle antibody and lowered sTSH during March 1995 to February 1998. Their smears were classified into 4 types according to the degree of degeneration of adenoidal cell and lymphocyte invasion.

RESULTS

Hyperthyroidism was observed in 5 cases, I type in 9, II type in 9, III type in 4, and IV type in 31 (53%).

CONCLUSIONS

FNB is helpful in diagnosis of hyperthyroidism.

Fanconi anemia proteins FANCA, FANCC, and FANCG/XRCC9 interact in a functional nuclear complex

Fanconi anemia (FA) is an autosomal recessive cancer susceptibility syndrome with at least eight complementation groups (A to H). Three FA genes, corresponding to complementation groups A, C, and G, have been cloned, but their cellular function remains unknown. We have previously demonstrated that the FANCA and FANCC proteins interact and form a nuclear complex in normal cells, suggesting that the proteins cooperate in a nuclear function. In this report, we demonstrate that the recently cloned FANCG/XRCC9 protein is required for binding of the FANCA and FANCC proteins. Moreover, the FANCG protein is a component of a nuclear protein complex containing FANCA and FANCC. The amino-terminal region of the FANCA protein is required for FANCG binding, FANCC binding, nuclear localization, and functional activity of the complex. Our results demonstrate that the three cloned FA proteins cooperate in a large multisubunit complex. Disruption of this complex results in the specific cellular and clinical phenotype common to most FA complementation groups.

Effects of nitric oxide inhibitor on prostacyclin biosynthesis in portal hypertensive rats

OBJECTIVE

To evaluate the effects of nitric oxide inhibitor on prostacyclin (PGI2) biosynthesis and the role of PGI2 in hyperhemodynamics of portal hypertension.

METHODS

Sprague Dawley rats were divided into four groups: intrahepatic portal hypertension (IHPH) by injection of CCl4, prehepatic portal hypertension (PHPH) by stenosis of the portal vein, end-to-side portacaval shunt (PCS), and sham-operated controls (SO). Animals of each group were subdivided into 2 groups: systemic administration of nitric oxide inhibitor L-NMMA and vehicle. The radioactive microsphere method was used for hemodynamic study. The level of plasma PGI2 (6-keto-PGF1 alpha) was measured by radioimmunoassay.

RESULTS

The characteristics of hyperdynamic circulatory state including increased cardiac output and splanchnic blood flow, decreased mean arterial blood pressure, total peripheral vascular resistance, and splanchnic vascular resistance were observed in IHPH, PHPH and PCS rats. The magnitude of hyperhemodynamics was in the order of PCS > PHPH > IHPH rats. The hyperdynamic circulatory state in IHPH, PHPH and PCS rats could be effectively reversed by L-NMMA to the baseline values of hemodynamics in SO rats. The baseline concentrations of plasma 6-keto-PGF1 alpha (ng/ml) in PHPH, IHPH, PCS, and SO rats were 6.93 +/- 2.43, 5.09 +/- 2.27, 2.36 +/- 1.01 and 1.56 +/- 0.61, respectively. The concentrations of plasma 6-Keto-PGF1 alpha in PHPH, IHPH and PCS rats were significantly higher than those in SO rats. Moreover, the concentrations were significantly higher in PHPH and IHPH rats than in PCS rats (P < 0.05). After administration of L-NMMA, the concentrations of plasma 6-Keto-PGF1 alpha (ng/ml) in PHPH, IHPH, PCS and SO rats were 7.69 +/- 2.98, 5.68 +/- 2.66, 5.50 +/- 0.79, 5.02 +/- 2.86, respectively. As compared to the baseline value, the concentrations of 6-keto-PGF1 alpha rats were slightly increased in IHPH, PHPH rats (P > 0.05), but significantly increased in PCS and SO rats (P < 0.05).

CONCLUSIONS

In this study, the hyperdynamic circulatory state in portal hypertensive rats and portacaval shunt rats was completely reversed by L-NNMA to normal, but the level of 6-keto-PGF1 alpha was still elevated. The results indicate that PGI2 is not involved in hyperhemodynamics of portal hypertension.

Changes and challenges in China. Is the "open policy" closing doors in Chinese hospitals?

Since 1978, China's economic reforms and her pursuit of modern technology have significantly opened the scope of her hospital services and financing. While the decentralization and higher incomes have given Chinese hospitals new freedoms, they have also raised the specter of new limitations on access to healthcare. The authors review these changes and consider what the future holds for the Chinese hospital system.

The molecular and cellular biology of Fanconi anemia

Fanconi anemia is a rare autosomal recessive disease characterized by multiple congenital abnormalities, bone marrow failure, and cancer susceptibility. The mean age of onset of anemia is 8 years, and the mean survival is 16 years. Death usually results from complications of bone marrow failure. Considerable progress in Fanconi anemia research has resulted from the recent identification and cloning of three Fanconi anemia genes. The current review describes the structure and function of the Fanconi anemia genes and describes the role of the encoded Fanconi anemia proteins in a cellular pathway controlling chromosome stability.

Vanilloid receptor agonists potentiate the in vivo local anesthetic activity of percutaneously injected site 1 sodium channel blockers

BACKGROUND

Capsaicin, the pungent ingredient in chili peppers, is a vanilloid with noxious and analgesic effects that inhibits tetrodotoxin-resistant sodium currents. Because tetrodotoxin-resistant currents are found primarily in small-diameter nociceptor afferents of the peripheral nerves, their inhibition may lead to selective analgesia. Therefore, the authors evaluated the interactions between tetrodotoxin, a site 1 sodium channel blocker, and capsaicin on nerve blockade in vivo.

METHODS

Percutaneous sciatic nerve injections with 0 to 9.9 mM capsaicin, 0 to 120 microM tetrodotoxin, or both were administered to male Sprague-Dawley rats. Thermal nociceptive and motor blockade were measured. Data were expressed as medians with 25th and 75th percentiles.

RESULTS

Capsaicin produced a transient increase in thermal latency with no effect on motor strength. Tetrodotoxin reduced motor strength for a longer duration than nociception. The interaction between tetrodotoxin and capsaicin was synergistic, as evidenced by (1) supraadditive prolongation of both nociceptive and motor block, with the effect of capsaicin reversed by the vanilloid antagonist capsazepine, and (2) synergism in the frequency that rats achieved maximal block shown by isobolographic analysis. The combination of tetrodotoxin and capsaicin showed less motor predominance than tetrodotoxin did alone. Similar interactions were found between tetrodotoxin and resiniferatoxin (another vanilloid), and between capsaicin and saxitoxin (another site 1 sodium channel blocker), but much less so between bupivacaine and capsaicin.

CONCLUSIONS

Site 1 sodium channel blockers and vanilloids have synergistic effects on nerve blockade in vivo. These interactions may be useful in developing prolonged local anesthetics and elucidating mechanisms of functionally selective nerve blockade.

Boo, a novel negative regulator of cell death, interacts with Apaf-1

In this report, we describe the cloning and characterization of Boo, a novel anti-apoptotic member of the Bcl-2 family. The expression of Boo was highly restricted to the ovary and epididymis implicating it in the control of ovarian atresia and sperm maturation. Boo contains the conserved BH1 and BH2 domains, but lacks the BH3 motif. Like Bcl-2, Boo possesses a hydrophobic C-terminus and localizes to intracellular membranes. Boo also has an N-terminal region with strong homology to the BH4 domain found to be important for the function of some anti-apoptotic Bcl-2 homologues. Chromosomal localization analysis assigned Boo to murine chromosome 9 at band d9. Boo inhibits apoptosis, homodimerizes or heterodimerizes with some death-promoting and -suppressing Bcl-2 family members. More importantly, Boo interacts with Apaf-1 and forms a multimeric protein complex with Apaf-1 and caspase-9. Bak and Bik, two pro-apoptotic homologues disrupt the association of Boo and Apaf-1. Furthermore, Boo binds to three distinct regions of Apaf-1. These results demonstrate the evolutionarily conserved nature of the mechanisms of apoptosis. Like Ced-9, the mammalian homologues Boo and Bcl-xL interact with the human counterpart of Ced-4, Apaf-1, and thereby regulate apoptosis.

Mechanism of overproduction of plasma prostacyclin in portal hypertensive rats

OBJECTIVE

To evaluate the role of increased portal pressure and portosystemic shunting in elevated level of prostacyclin (PGI2) in portal hypertension.

METHODS

Thirty-six male Sprague-Dawley rats were divided into four groups: prehepatic portal hypertension (PHPH, 8 rats), intrahepatic portal hypertension (IHPH, 9), end-to-side portacaval shunt (PCS, 8), and sham-operated controls (SO, 11). Two weeks after surgery, free portal pressure (FPP) was measured; systemic and splanchnic hemodynamics was studied by radioactive microsphere technique and blood sample from the femoral artery was obtained to measure the level of plasma 6-keto-PGF1 alpha with radioimmunoassay.

RESULTS

The FPP (mmHg) in IHPH, PHPH, PCS and SO rats was 13.10 +/- 1.02, 12.10 +/- 1.52, 3.0 +/- 0.82 and 6.86 +/- 0.69, respectively. The value of FPP was significantly increased in IHPH, PHPH rats and significantly decreased in PCS rats when compared to SO rats. Cardiac index (CI) and portal venous inflow (PVI) were in the order of PCS > PHPH > IHPH > SO rats. Portosystemic shunting (PSS) in PCS, PHPH, IHPH was 99.7 +/- 0.29%, 76.02 +/- 20.62% and 30.34 +/- 10.18%, respectively. The concentrations of plasma 6-keto-PGF1 alpha (ng/ml) in PHPH, IHPH, PCS and SO rats were 6.93 +/- 2.43, 5.09 +/- 2.27, 2.36 +/- 1.01 and 1.56 +/- 0.61, respectively. The concentrations of plasma PGI2 in PHPH, IHPH and PCS rats were significantly higher than those in SO rats. Furthermore, the concentrations of plasma PGI2 in PHPH and IHPH rats were also significantly higher than those in PCS rats. Moreover, a closed positive correlation existed between plasma PGI2 and FPP (r = 0.67, P < 0.001).

CONCLUSIONS

The results of the present study suggest that the elevated PGI2 in portal hypertension is mainly due to the overproduction of PGI2 in vascular epithelium cells induced by increased portal pressure, whereas portosystemic shunting and liver dysfunction play a secondary role. In addition, the results of this study do not support that PGI2 mediated the hyperhemodynamics in portal hypertension.

[Interleukin-6 and its soluble receptors in human breast cancer]

OBJECTIVE

To study interleukin-6(IL-6) and its receptors in human breast cancer.

METHODS

Using ELISA method and ABC immunohistochemistry, IL-6 and its receptors were examined in 45 cases of breast cancer, 10 cases of benign breast diseases and 17 cases of healthy women.

RESULTS

High levels of serum IL-6 and its soluble receptors were frequently observed in breast cancer patients. The levels correlated with the stage and axillary lymph node involvement. The positive staining of IL-6, IL-6R alpha, gp130 were 68.9% in neoplasm tissue.

CONCLUSION

IL-6 and its soluble receptors may be important paramenters reflecting the biological behaviour and prognosis of breast cancer.

Modeling and analysis of a marine bacteriophage infection

A mathematical model for the marine bacteriophage infection is proposed and its essential mathematical features are analyzed. Since bacteriophage infection induces bacterial lysis which releases into the marine environment, on the average, 'b' viruses per cell, the parameter b epsilon (1, t infinity) or 'virus replication factor' is chosen as the main parameter on which the dynamics of the infection depends. We proved that a threshold b* exists beyond which the endemic equilibrium bifurcates from the free disease one. Still, for increasing b values the endemic equilibrium bifurcates toward a periodic solution. We proved that a compact attractor set omega within the positive cone exists and within omega the free disease equilibrium is globally stable whenever b < or = b*, whereas it becomes a strong uniform repeller for b > b*. A concluding discussion with numerical simulation is then presented.

[Experimental study of the effect on growth of Schwann cell from chitin and chitosan in vitro]

In order to study the effect of chitin and chitosan on the growth of Schwann cell (SC) of rats in vitro, the SC was isolated from sciatic nerve and brachial plexus of new-born rats. After the enzymatic and mechanical dissociation, the cell suspension was vaccinated on chitin membrane and chitosan fluid-coated glass coverslips. Then, the growth of SC was examined at 1, 3, 7 days after culture under light microscope and scanning electron microscope. The results showed that 94 percent of the cell grown from was SC and only 6% was fibroblast (FB), while that of the control SC 71% and FB 29% in population. The number of SC in chitosan suspension was more than that in chitin. Therefore, the conclusion was that the chitin and chitosan was histocompatible to SC, and chitosan suspension was superior to chitin, and both could inhibit the growth of fibroblast.

[The role of nitric oxide in hyperdynamic circulation in portal hypertensive rats]

OBJECTIVE

To evaluate the role of nitric oxide (NO) in hyper-hemodynamics in portal hypertension, we investigated the effects of nitric oxide synthase inhibitor L-NMMA with or without L-arginine, the substrate for enzyme NO synthase on the systemic and splanchnic hemodynamics in portal hypertensive rats.

METHOD

Ninety-seven male Sprague-Dawley rats were divided into four groups: intrahepatic portal hypertension (IHPH, n = 23) by injection of CCl4, prehepatic portal hypertension (PHPH, n = 26) by stenosis of the portal vein, end-to-side portacaval shunt (PCS, n = 23), and sham-operated controls (SO, n = 25). Animals of each group were divided into three subgroups: systemic administration of L-NMMA (50 mg/kg BW, 1 ml), L-NMMA (50 mg/kg BW, 0.5 ml) plus L-arginine (30 mg/kg BW, 0.5 ml), and normal saline solution (1 ml). The radioactive microsphere method was used for hemodynamic study.

RESULT

There was the characteristic of hyperdynamic circulatory state including increased cardiac output and splanchnic blood flow, decreased mean arterial blood pressure, total peripheral vascular resistance and splanchnic vascular resistance in IHPH, PHPH and PCS rats. The hyperdynamic circulatory state in IHPH, PHPH and PCS rats could be effectively reversed by L-NMMA to the resting values of hemodynamics in SO rats, but not the levels after administration of L-NMMA in SO rats, indicating that there is excessive production of NO in portal hypertensive and PCS rats. Administration of L-arginine counterbalanced the effects of L-NMMA on hyperdynamic circulatory state in portal hypertensive and PCS rats.

CONCLUSION

NO is an important mediator of hyperdynamic circulation in portal hypertension.

The role for endothelin in mesangial proliferative glomerulonephritis

To understand the effect of endothelin (ET) on the mesangium and matrix proliferation on the basis of hyperlipidemia, the model of mesangial proliferative glomerulonephritis (MSPGN) was established by intravenously giving calf serum albumin (250 mg/L) to the rabbits fed on feed containing 1% cholesterol for 4-8 weeks. Our results showed that in the 4th week of the experiment, the ET level in experiment group was significantly higher than that of normal controls (P < 0.01) and the pathological examination revealed development of MSPGN. In the 8th week of the experiment, the ET level was further elevated and pathological study demonstrated local glomerular sclerosis and infiltration of lymphocytes of interstitia. We are led to conclude that ET, as a newly identified hormone, is involved in the pathogenesis and development of MSPGN and acts as an important regulator in the proliferation of mesangium and accumulation of matrix of basal membrane.

Roles of phospholipase C beta2 in chemoattractant-elicited responses

The physiological roles of phospholipase C (PLC) beta2 in hematopoiesis, leukocyte function, and host defense against infection were investigated using a mouse line that lacks PLC beta2. PLC beta2 deficiency did not affect hematopoiesis, but it blocked chemoattractant-induced Ca2+ release, superoxide production, and MAC-1 up-regulation in neutrophils. In view of these effects, it was surprising that the absence of PLC beta2 enhanced chemotaxis of different leukocyte populations and sensitized the in vivo response of the PLC beta2-deficient mice to bacteria, viruses, and immune complexes. These data raise questions about the roles that PLC beta2 may play in signal transduction induced by chemoattractants in leukocytes.

alpha-Latrotoxin stimulates exocytosis by the interaction with a neuronal G-protein-coupled receptor

alpha-Latrotoxin is a potent stimulator of neurosecretion. Its action requires extracellular binding to high affinity presynaptic receptors. Neurexin I alpha was previously described as a high affinity alpha-latrotoxin receptor that binds the toxin only in the presence of calcium ions. Therefore, the interaction of alpha-latrotoxin with neurexin I alpha cannot explain how alpha-latrotoxin stimulates neurotransmitter release in the absence of calcium. We describe molecular cloning and functional expression of the calcium-independent receptor of alpha-latrotoxin (CIRL), which is a second high affinity alpha-latrotoxin receptor that may be the major mediator of alpha-latrotoxin's effects. CIRL appears to be a novel orphan G-protein-coupled receptor, a member of the secretin receptor family. In contrast with other known serpentine receptors, CIRL has two subunits of the 120 and 85 kDa that are the result of endogenous proteolytic cleavage of a precursor polypeptide. CIRL is found in brain where it is enriched in the striatum and cortex. Expression of CIRL in chromaffin cells increases the sensitivity of the cells to the effects of alpha-latrotoxin, demonstrating that this protein is functional in coupling to secretion. Syntaxin, a component of the fusion complex, copurifies with CIRL on an alpha-latrotoxin affinity column and forms stable complexes with this receptor in vitro. Interaction of CIRL with a specific presynaptic neurotoxin and with a component of the docking-fusion machinery suggests its role in regulation of neurosecretion.

[SMC proliferation and its distribution in autologous vein grafts]

SMC proliferation in intimal hyperplasia is a major cause of graft failure. We induced experimental jugular vein to aortic autograft in 120 Wistar rats, and analyzed the SMC proliferation and its distribution in the graft by flow cytometry (FCM) and immunohistochemistry of proliferating cellular nuclear antigen (PCNA) from 2 hours, 6 hours, 24 hours to 1 week, 2 weeks and 4 weeks. Although the number was not apparently increased in autologous vein graft at early stage, SMC proliferation had started. At 1 week after transplantation, the activity of SMC proliferation increased to a maximum, and returned to baseline level 4 weeks. At early stage, the distribution of SMC proliferation located in the media, but at middle stage, both intima and media all presented a relatively higher proliferative activity. The intima formation occurred by the migration of a large population and the proliferation of a relatively small subpopulation of SMC. Therefore, control of SMC proliferation, and migration of autologous vein grafts must be within two weeks after transplantation.

Pertussis toxin-sensitive activation of phospholipase C by the C5a and fMet-Leu-Phe receptors

Signal transduction pathways that mediate C5a and fMet-Leu-Phe (fMLP)-induced pertussis toxin (PTx)-sensitive activation of phospholipase C (PLC) have been investigated using a cotransfection assay system in COS-7 cells. The abilities of the receptors for C5a and fMLP to activate PLC beta2 and PLC beta3 through the Gbetagamma subunits of endogenous Gi proteins in COS-7 cells were tested because both PLC beta2 and PLC beta3 were shown to be activated by the betagamma subunits of G proteins in in vitro reconstitution assays. Neither of the receptors can activate endogenous PLC beta3 or recombinant PLC beta3 in transfected COS-7 cells. However, both receptors can clearly activate PLC beta2 in a PTx-sensitive manner, suggesting that the receptors may interact with endogenous PTx-sensitive G proteins and activate PLC beta2 probably through the Gbetagamma subunits. These findings were further corroborated by the results that PLC beta3 could only be slightly activated by Gbeta1gamma1 or Gbeta1gamma5 in the cotransfection assay, whereas the Gbetagamma subunits strongly activated PLC beta2 under the same conditions. PLC beta3 can be activated by Galphaq, Galpha11, and Galpha16 in the cotransfection assay. In addition, the Ggamma2 and Ggamma3 mutants with substitution of the C-terminal Cys residue by a Ser residue, which can inhibit wild type Gbetagamma-mediated activation of PLC beta2, were able to inhibit C5a or fMLP-mediated activation of PLC beta2. These Ggamma mutants, however, showed little effect on m1-muscarinic receptor-mediated PLC activation, which is mediated by the Gq class of G proteins. These results all confirm that the Gbetagamma subunits are involved in PLC beta2 activation by the two chemoattractant receptors and suggest that in COS-7 cells activation of PLC beta3 by Gbetagamma may not be the primary pathway for the receptors.

Identification of a phospholipase C beta2 region that interacts with Gbeta-gamma

To delineate the phospholipase C (PLC; EC 3.1.4.3) beta2 sequences involved in interactions with the beta-gamma subunits of G proteins, we prepared a number of mammalian expression plasmids encoding a series of PLC beta2 segments that span the region from the beginning of the X box to the end of the Y box. We found the sequence extending from residue Glu-435 to residue Val-641 inhibited Gbeta-gamma-mediated activation of PLC beta2 in transfected COS-7 cells. This PLC beta2 sequence also inhibited ligand-induced activation of PLC in COS-7 cells cotransfected with cDNAs encoding the complement component C5a receptor and PLC beta2 but not in cells transfected with the alpha1B-adrenergic receptor, suggesting that the PLC beta2 residues (Glu-435 to Val-641) inhibit the Gbeta-gamma-mediated but not the Galpha-mediated effect. The inhibitory effect on Gbeta-gamma-mediated activation of PLC beta2 may be the result of the interaction between Gbeta-gamma and the PLC beta2 fragment. This idea was confirmed by the observation that a fusion protein comprising these residues (Glu-435 to Val-641) of PLC beta2 and glutathione S-transferase (GST) bound to Gbeta-gamma in an in vitro binding assay. The Gbeta-gamma-binding region was further narrowed down to 62 amino acids (residues Leu-580 to Val-641) by testing fusion proteins comprising various PLC beta2 sequences and GST in the in vitro binding assay.

Selective G protein coupling by C-C chemokine receptors

The C-C chemokines are major mediators of chemotaxis of monocytes and some T cells in inflammatory reactions. The pathways by which the C-C chemokine receptors activate phospholipase C (PLC) were investigated in cotransfected COS-7 cells. The C-C chemokine receptor-1 (CKR-1), the MCP-1 receptor-A (MCP-1Ra), and MCP-1Rb can reconstitute ligand-induced accumulation of inositol phosphates with PLC beta2 in a pertussis toxin-sensitive manner, presumably through G beta gamma released from the Gi proteins. However, these three receptors demonstrated different specificity in coupling to the alpha subunits of the Gq class. While none of the receptors can couple to Galphaq/11, MCP-1Rb can couple to both Galpha14 and Galpha16, but its splicing variant, MCP-1Rb, cannot. Since MCP-1Ra and -b differ only in their C-terminal intracellular domains, the C-terminal ends of MCP-1Rs determine G protein coupling specificity. CKR-1 can couple to Galpha14 but not to Galpha16, suggesting some of the C-C chemokine receptors, unlike the C-X-C chemokine receptors, discriminate against Galpha16, a hematopoietic-specific Galpha subunit. The intriguing specificity in coupling of the Gq class of G proteins implies that the chemokines may be involved in some distinct functions in vivo. The commonality of the chemokine receptors in coupling to the Gi-Gbetagamma-PLC beta2 pathway provides a potential target for developing broad spectrum anti-inflammatory drugs.