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C L Carpenter

Publications and source records attributed to C L Carpenter.

At least 19 recordsLinked to original sources
PubMed2004

Btk-dependent regulation of phosphoinositide synthesis.

Activation of the BCR (B cell antigen receptor) stimulates the production of both PtdIns(3,4,5) P3 and Ins(1,4,5) P3. PtdIns(3,4,5) P3 and Ins(1,4,5) P3 are generated from a common substrate, PtdIns(4,5) P2. In some systems, continuous PtdIns(4,5) P2 synthesis is necessary for maximal Ins(1,4,5) P3 production, but whether this is true for the BCR, and whether PtdIns(4,5) P2 synthesis is regulated following BCR activation, are not known. We found that Btk (Bruton's tyrosine kinase), a member of the Tec family of cytoplasmic protein tyrosine kinases, is constitutively associated with PIP5Ks (phosphatidylinositol 4-phosphate 5-kinases), the enzymes that synthesize PtdIns(4,5) P2. Btk functions as a shuttle to bring PIP5K to the plasma membrane as a means of stimulating PtdIns(4,5) P2 synthesis. The Btk-PIP5K complex appears to localize to lipid rafts. This complex provides a novel shuttling mechanism that allows Btk to regulate the production of the substrate required by both its upstream activator phosphoinositide 3-kinase and its downstream target phospholipase Cgamma2.

Agammaglobulinaemia Tyrosine Kinase↗
PubMed2001

LKB1 associates with Brg1 and is necessary for Brg1-induced growth arrest.

Inactivating mutations in the serine-threonine kinase LKB1 (STK11) are found in most patients with Peutz-Jeghers syndrome; however the function of LKB1 is unknown. We found that LKB1 binds to and regulates brahma-related gene 1 (Brg1), an essential component of chromatin remodeling complexes. The association requires the N terminus of LKB1 and the helicase domain of Brg1 and LKB1 stimulates the ATPase activity of Brg1. Brg1 expression in SW13 cells induces the formation of flat cells indicative of cell cycle arrest and senescence. Expression of a kinase-dead mutant of LKB1, SL26, in SW13 cells blocks the formation of Brg1-induced flat cells, indicating that LKB1 is required for Brg1-dependent growth arrest. The inability of mutants of LKB1 to mediate Brg1-dependent growth arrest may explain the manifestations of Peutz-Jeghers syndrome.

AMP-Activated Protein Kinase Kinases↗
PubMed2001

Vav2 is required for cell spreading.

Vav2 is a widely expressed Rho family guanine nucleotide exchange factor highly homologous to Vav1 and Vav3. Activated versions of Vav2 are transforming, but the normal function of Vav2 and how it is regulated are not known. We investigated the pathways that regulate Vav2 exchange activity in vivo and characterized its function. Overexpression of Vav2 activates Rac as assessed by both direct measurement of Rac-GTP and cell morphology. Vav2 also catalyzes exchange for RhoA, but does not cause morphologic changes indicative of RhoA activation. Vav2 nucleotide exchange is Src-dependent in vivo, since the coexpression of Vav2 and dominant negative Src, or treatment with the Src inhibitor PP2, blocks both Vav2-dependent Rac activation and lamellipodia formation. A mutation in the pleckstrin homology (PH) domain eliminates exchange activity and this construct does not induce lamellipodia, indicating the PH domain is necessary to catalyze nucleotide exchange. To further investigate the function of Vav2, we mutated the dbl homology (DH) domain and asked whether this mutant would function as a dominant negative to block Rac-dependent events. Studies using this mutant indicate that Vav2 is not necessary for platelet-derived growth factor- or epidermal growth factor-dependent activation of Rac. The Vav2 DH mutant did act as a dominant negative to inhibit spreading of NIH3T3 cells on fibronectin, specifically by blocking lamellipodia formation. These findings indicate that in fibroblasts Vav2 is necessary for integrin, but not growth factor-dependent activation of Rac leading to lamellipodia.

3T3 Cells↗
PubMed2000

Type Ialpha phosphatidylinositol-4-phosphate 5-kinase mediates Rac-dependent actin assembly.

Action polymerization is essential for a variety of cellular processes including movement, cell division and shape change. The induction of actin polymerization requires the generation of free actin filament barbed ends, which results from the severing or uncapping of pre-existing actin filaments [1] [2], or de novo nucleation, initiated by the Arp2/3 complex [3] [4] [5] [6] [7]. Although little is known about the signaling pathways that regulate actin assembly, small GTPases of the Rho family appear to be necessary [8] [9] [10] [11]. In thrombin-stimulated platelets, the Rho family GTPase Rac1 induces actin polymerization by stimulating the uncapping of actin filament barbed ends [2]. The mechanism by which Rac regulates uncapping is unclear, however. We previously demonstrated that Rac interacts with a type I phosphatidylinositol-4-phosphate 5-kinase (PIP 5-kinase) in a GTP-independent manner [12] [13]. Because PIP 5-kinases synthesize phosphatidylinositol-4,5-bisphosphate (PI(4,5)P(2)), a lipid that dissociates capping proteins from the barbed ends of actin filaments [14] [15] [16], they are good candidates for mediating the effects of Rac on actin assembly. Here, we have identified the Rac-associated PIP 5-kinase as the PIP 5-kinase isoforms alpha and beta. When added to permeabilized platelets, PIP 5-kinase alpha induced actin filament uncapping and assembly. In contrast, a kinase-inactive PIP 5-kinase alpha mutant failed to induce actin assembly and blocked assembly stimulated by thrombin or Rac. Furthermore, thrombin- or Rac-induced actin polymerization was inhibited by a point mutation in the carboxyl terminus of Rac that disrupts PIP 5-kinase binding. These results demonstrate that PIP 5-kinase alpha is a critical mediator of thrombin- and Rac-dependent actin assembly.

Actins↗
PubMed2000

Actin cytoskeleton and cell signaling.

The role of the actin cytoskeleton in the function of eukaryotic cells is ubiquitous. Regulation of actin polymerization allows cells to control their shape, to move, divide, secrete, and phagocytose. Actin filaments provide strength, connections to other cells and the extracellular matrix, paths for intracellular transport and a scaffold for generating force. Recently, a number of signal transduction pathways have been identified that regulate actin polymerization and contractility. GTP-binding proteins, protein kinases, phosphoinositide kinases, and protein phosphatases all play important roles in determining the location and extent of actin polymerization and contractility of actin/myosin filaments. These pathways allow cells to respond to extracellular signals to regulate movement, the tone of vascular smooth muscle cells, secretion, and phagocytosis. Some pathogens use signal transduction pathways that regulate actin polymerization to invade cells. The signal transduction pathways that regulate actin-dependent events are the focus of this review.

Actins↗
PubMed2000

Atypical protein kinases Clambda and -zeta associate with the GTP-binding protein Cdc42 and mediate stress fiber loss.

Both the Rho family of low-molecular-weight GTP-binding proteins and protein kinases C (PKCs) mediate responses to a variety of extracellular and intracellular signals. They share many downstream targets, including remodeling of the actin cytoskeleton, activation of p70(S6) kinase and c-jun N-terminal kinase (JNK), and regulation of transcription and cell proliferation. We therefore investigated whether Rho family GTP-binding proteins bind to PKCs. We found that Cdc42 associates with atypical PKCs (aPKCs) PKCzeta and -lambda in a GTP-dependent manner. The regulatory domain of the aPKCs mediates the interaction. Expression of activated Cdc42 results in the translocation of PKClambda from the nucleus into the cytosol, and Cdc42 and PKClambda colocalize at the plasma membrane and in the cytoplasm. Expression of activated Cdc42 leads to a loss of stress fibers, as does overexpression of either the wild type or an activated form of PKClambda. Kinase-dead PKClambda and -zeta constructs acted as dominant negatives and restored stress fibers in cells expressing the activated V12 Cdc42 mutant, indicating that Cdc42-dependent loss of stress fibers requires aPKCs. Kinase-dead PKClambda and -zeta and dominant-negative N17 Cdc42 also blocked Ras-induced loss of stress fibers, suggesting that this pathway may also be important for Ras-dependent cytoskeletal changes. N17 Rac did not block Ras-induced loss of stress fibers, nor did kinase-dead PKClambda block V12 Rac-stimulated loss of stress fibers. These results indicate that Cdc42 and Rac use different pathways to regulate stress fibers.

Animals↗
PubMed2000

Body size, physical activity, and breast cancer hormone receptor status: results from two case-control studies.

We evaluated whether our previous reports of increased postmenopausal breast cancer risk with higher body mass index (BMI) or of reduced premenopausal and postmenopausal breast cancer risk with higher physical activity levels varied according to the tumor's estrogen receptor (ER) and progesterone receptor (PR) status. Participants enrolled in either of two population-based case-control studies in Los Angeles County, California: one of premenopausal women (ages < or = 40 years), and one of postmenopausal women (ages 55-64 years). Case participants were diagnosed for the first time with in situ or invasive breast cancer from 7/1/83 through 12/31/88 (premenopausal women) or from 3/1/87 through 12/31/89 (postmenopausal women). Joint ER/PR status was collected for 424 premenopausal and 760 postmenopausal case participants. The analysis included 714 premenopausal and 1091 postmenopausal age-matched, race-matched (white or Hispanic), parity-matched (premenopausal women only), and residential neighborhood-matched control participants. Among the postmenopausal women, obesity was associated with an increased odds of ER+/PR+ breast cancer (odds ratio, 2.45 for women in the highest versus the lowest body mass index quartile; 95% confidence interval, 1.73-3.47). Body mass index was associated with neither ER-/PR- tumors among the postmenopausal women nor with any ER/PR subgroup among the premenopausal women. For both premenopausal and postmenopausal women, higher recreational physical activity levels (> or = 17.6 MET-hours/week versus no activity) were associated with a 30-60% reduction in risk of nearly all ER/PR subtypes, although the associations were generally of borderline statistical significance. Examining these potentially modifiable breast cancer risk factors by tumor ER and PR status may provide us with greater insight into breast cancer etiology and the mechanisms underlying the risk factor associations.

Adult↗
PubMed2000

Blunt chest trauma in the elderly patient: how cardiopulmonary disease affects outcome.

Blunt trauma patients with rib fractures have significant risk of morbidity and mortality. The risk of complications increases with age and cardiopulmonary disease. We reviewed our experience at a community hospital Level II trauma center over a 5-year period. A review of the trauma registry revealed 62 patients over the age of 65 with multiple rib fractures and no associated injuries. Thirty-one patients with cardiopulmonary disease (CPD+) were compared with 31 patients without cardiopulmonary disease (CPD-). Charts were reviewed for morbidity, mortality, the need to upgrade level of care (readmission to the hospital or intensive care unit), and length of hospitalization. Complications occurred in 17 of 31 CPD+ patients and in four of 31 CPD- patients (P < 0.001). The only three deaths were in CPD+ patients. Ten CPD+ patients and four CPD- patients required an upgrade in the level of care (P < 0.05). The CPD+ patients had longer hospitalization than the CPD- patients: 8.5 versus 4.3 days (P < 0.05). We conclude that elderly patients with multiple rib fractures and cardiopulmonary disease are at significant risk for complications that result in readmission to the hospital and intensive care unit and prolonged length of hospitalization. Admission to the intensive care unit with attention to cardiac and pulmonary status upon transfer to the ward is warranted.

Age Factors↗
PubMed1999

Prevalence of HIV-1 among recent arrestees in Los Angeles County, California: serial cross-sectional study, 1991-1995.

Injection drug users (IDU), crack smokers, and commercial sex workers engage in illegal activities that place them at risk for HIV infection. The marginalized nature of these groups often limits use of customary sampling methods to assess HIV prevalence. We tested urine samples of recent arrestees to evaluate HIV prevalence of at-risk populations that are difficult to access using standard surveillance methods. We tested for HIV-1 antibodies in urine specimens of recent Los Angeles County (California, U.S.A.) arrestees as part of the Drug Use Forecasting (DUF) Program funded by the U. S. National Institute of Justice. Data are presented for 5 years of a serial cross-sectional study of arrestees. Results from 1991 through 1995 indicate a slight HIV prevalence increase among crack smokers (from 4% to 6%). Prevalence estimates were relatively stable for IDU (6%), male (3%) and female arrestees (3%), arrestees who share needles (9%), and commercial sex workers (6%). HIV status was independently associated with injection drug use, crack smoking, and ever having exchanged sex for money or drugs. Prevalence of HIV among arrestee subgroups may reflect prevalence in the community. However the benefit of using the DUF sample must be weighed against bias introduced from using nonrandom samples to estimate prevalence.

Crack Cocaine↗
PubMed1999

c-Jun is a JNK-independent coactivator of the PU.1 transcription factor.

The ETS domain transcription factor PU.1 is necessary for the development of monocytes and regulates, in particular, the expression of the monocyte-specific macrophage colony-stimulating factor (M-CSF) receptor, which is critical for monocytic cell survival, proliferation, and differentiation. The bZIP transcription factor c-Jun, which is part of the AP-1 transcription factor complex, is also important for monocytic differentiation, but the monocyte-specific M-CSF receptor promoter has no AP-1 consensus binding sites. We asked the question of whether c-Jun could promote the induction of the M-CSF receptor by collaborating with PU.1. We demonstrate that c-Jun enhances the ability of PU.1 to transactivate the M-CSF receptor promoter as well as a minimal thymidine kinase promoter containing only PU.1 DNA binding sites. c-Jun does not directly bind to the M-CSF receptor promoter but associates via its basic domain with the ETS domain of PU.1. Consistent with our observation that AP-1 binding does not contribute to c-Jun coactivation is the observation that the activation of PU.1 by c-Jun is blocked by overexpression of c-Fos. Phosphorylation of c-Jun by c-Jun NH2-terminal kinase on Ser-63 and -73 does not alter the ability of c-Jun to enhance PU.1 transactivation. Activated Ras enhances the transcriptional activity of PU.1 by up-regulating c-Jun expression without changing the phosphorylation pattern of PU.1. The activation of PU.1 by Ras is blocked by a mutant c-Jun protein lacking the basic domain. The expression of this mutant form of c-Jun also completely blocks 12-O-tetradecanoylphorbol-13-acetate-induced M-CSF receptor promoter activity during monocytic differentiation. We propose therefore that c-Jun acts as a c-Jun NH2-terminal kinase-independent coactivator of PU.1, resulting in M-CSF receptor expression and development of the monocytic lineage.

Animals↗
PubMed1999

Lipid kinases are novel effectors of the GTPase Rac1.

We have found that a complex consisting of a type I PIPK and a DGK associates with the GTPase Rac1. Binding of the lipid kinase complex is through the C-terminus of Rac. Complex formation is augmented in the presence of specific phospholipids. The complex also associates with Rho GDI, through Rac. Based on the role of PtdIns-4,5-P2 in regulating proteins that influence actin structures we propose that the Rac-associated lipid kinase complex functions to generate locally high concentrations of PtdIns-4,5-P2 in a Rac-dependent manner. There are many possible roles PtdIns-4,5-P2 might play. A likely role is binding to barbed-end actin capping proteins. This would release the capping protein, providing free barbed ends for actin polymerization. Uncapping would occur at the membrane so that additional actin polymerization would result in membrane protrusions and lamellapodia, in a Brownian ratchet model. It is also possible that PtdIns-4,5-P2 has other roles, such as promoting the release of G actin from profilin or promoting the cross-linking of actin or its anchorage to the plasma membrane. Studies are currently underway to determine the role of this lipid kinase complex in Rac signaling and actin regulation in vivo.

Actins↗
PubMed1999

Mentholated cigarette smoking and lung-cancer risk.

PURPOSE: Menthol smoking may lead to a greater increase in lung-cancer risk than smoking of nonmentholated cigarettes. Mentholation of cigarettes adds additional carcinogenic components to cigarette smoke and increases retention times for cigarette smoke in the lungs. Only two epidemiologic studies have been conducted on menthol smoking and lung cancer, and their results are conflicting. Of note, African American males have much higher rates of lung cancer than Caucasian males despite smoking fewer cigarettes per day. Because the consumption of menthol cigarettes is much more frequent among African Americans, it is of interest to examine the possible association between menthol smoking and lung-cancer risk in this population. METHODS: We examined the association between menthol cigarette smoking and lung-cancer risk among smokers by comparing 337 incident cases of lung cancer with 478 population controls enrolled in a case-control study of lung cancer. Information on smoking history and other known and potential risk factors for lung cancer, including dietary intake, was obtained by in-person interviews. RESULTS: The adjusted odds ratios did not differ appreciably between smokers of mentholated cigarettes versus exclusive nonmentholated cigarette smokers in the overall study group of smokers. The odds ratio (OR) for 32 pack-years or more of mentholated vs. nonmentholated cigarettes was 0.90 (95% confidence interval (CI) = 0.38-2.12) in African Americans and 1.06 (95% CI = 0.47-2.36) in Caucasians, and did not differ for either ethnic group (p = 0.98). CONCLUSIONS: Our results suggest that the lung-cancer risk from smoking mentholated cigarettes resembles the risk from smoking non-mentholated cigarettes. Our data do not support the hypothesis that the increased risk of lung cancer among African Americans is due to the increased prevalence of menthol smoking.

Adult↗
PubMed1999

Lifetime exercise activity and breast cancer risk among post-menopausal women.

Lifetime exercise activity has been linked to breast cancer risk among young women. However, no study has specifically evaluated whether lifetime exercise activity is related to the breast cancer risk of post-menopausal women. We conducted a population-based case-control study of post-menopausal white women (1123 newly diagnosed cases and 904 healthy controls) aged 55-64 who lived in Los Angeles County, California, USA to evaluate this relationship. Although neither exercise activity from menarche to age 40 years, nor exercise after age 40 separately predicted breast cancer risk, risk was lower among women who had exercised each week for at least 17.6 MET-hours (metabolic equivalent of energy expenditure multiplied by hours of activity) since menarche than among inactive women (odds ratio (OR) = 0.55; 95% confidence interval (CI) 0.37-0.83). Exercise activity was not protective for women who gained considerable (> 17%) weight during adulthood. However, among women with more stable weight, breast cancer risk was substantially reduced for those who consistently exercised at high levels throughout their lifetime (OR = 0.42; 95% CI 0.24-0.75), those who exercised more than 4 h per week for at least 12 years (OR = 0.59; 95% CI 0.40-0.88), and those who exercised vigorously (24.5 MET-hours per week) during the most recent 10 years (OR = 0.52; 95% CI 0.32-0.85). Strenuous exercise appears to reduce breast cancer risk among post-menopausal women who do not gain sizable amounts of weight during adulthood.

Adult↗
PubMed1998

Enhancement of phosphoinositide 3-kinase (PI 3-kinase) activity by membrane curvature and inositol-phospholipid-binding peptides.

The phosphorylation of phosphatidylinositol (PtdIns) on the 3' position of the inositol ring by phosphoinositide 3-kinase (PI 3-kinase) is shown to depend strongly on the curvature of liposomes containing a mixture of phosphatidylcholine (PtdCho) and PtdIns. Vesicles with an average diameter of 50 nm are phosphorylated 100 times faster than chemically identical vesicles with an average diameter greater than 300 nm. The low reactivity of large vesicles is not due to the difference in vesicle number for large and small vesicles at constant total lipid, nor to occlusion of lipid surfaces in multilammelar structures, and can be reversed by addition of low (< 1:100) molar ratios of either the PtdIns transfer protein sec14p or a ten-residue peptide derived from the inositol-phospholipid-binding site of gelsolin. Similar measurements using PI 4-kinase showed a weak dependence on vesicle size. The strong dependence of PI 3-kinase function on membrane curvature suggests possible localization of PI 3-kinase activity at sites where clustering of receptors, for example, may locally deform the membrane, and suggests that once PI 3-kinase is localized and activated at surface sites, the reaction may become self-accelerating.

1-Phosphatidylinositol 4-Kinase↗
PubMed1998

Type I phosphatidylinositol-4-phosphate 5-kinases synthesize the novel lipids phosphatidylinositol 3,5-bisphosphate and phosphatidylinositol 5-phosphate.

Inositol phospholipids regulate a variety of cellular processes including proliferation, survival, vesicular trafficking, and cytoskeletal organization. Recently, two novel phosphoinositides, phosphatidylinositol-3,5-bisphosphate (PtdIns-3,5-P2) and phosphatidylinositol- 5-phosphate (PtdIns-5-P), have been shown to exist in cells. PtdIns-3,5-P2, which is regulated by osmotic stress, appears to be synthesized by phosphorylation of PtdIns-3-P at the D-5 position. No evidence yet exists for how PtdIns-5-P is produced in cells. Understanding the regulation of synthesis of these molecules will be important for identifying their function in cellular signaling. To determine the pathway by which PtdIns-3,5-P2 and Ptd-Ins-5-P might be synthesized, we tested the ability of the recently cloned type I PtdIns-4-P 5-kinases (PIP5Ks) alpha and beta to phosphorylate PtdIns-3-P and PtdIns at the D-5 position of the inositol ring. We found that the type I PIP5Ks phosphorylate PtdIns-3-P to form PtdIns-3,5-P2. The identity of the PtdIns-3,5-P2 product was determined by anion exchange high performance liquid chromatography analysis and periodate treatment. PtdIns-3,4-P2 and PtdIns-3,4,5-P3 were also produced from PtdIns-3-P phosphorylation by both isoforms. When expressed in mammalian cells, PIP5K Ialpha and PIP5K Ibeta differed in their ability to synthesize PtdIns-3,5-P2 relative to PtdIns-3,4-P2. We also found that the type I PIP5Ks phosphorylate PtdIns to produce PtdIns-5-P and phosphorylate PtdIns-3,4-P2 to produce PtdIns-3,4,5-P3. Our findings suggest that type I PIP5Ks synthesize the novel phospholipids PtdIns-3,5-P2 and PtdIns-5-P. The ability of PIP5Ks to produce multiple signaling molecules indicates that they may participate in a variety of cellular processes.

Animals↗
PubMed1998

Alcoholic beverage consumption and lung cancer risk among residents of Los Angeles County.

Although studies generally support a positive association between alcohol consumption and lung-cancer risk, the relationship between specific alcoholic beverages and lung-cancer risk has been inconsistent. We examined recent and past alcoholic beverage intake among 261 incident cases and 615 population controls enrolled in a lung-cancer case-control study of African Americans and Caucasians in Los Angeles County between 1991 and 1994. An in-person interview elicited information about past alcohol intake from ages 30 to 40 y, smoking, other lung-cancer risk factors, as well as recent intake of alcohol, and recent dietary intake. An association was observed between recent hard-liquor consumption and lung-cancer risk. The odds ratio (OR) for 1 or more drinks (1.5 oz or 0.051 mL) per day of hard liquor compared with infrequent liquor drinking (0-3 drinks per month), adjusted for smoking, the matching factors, saturated fat and other alcoholic beverages was 1.87 [95% confidence interval (CI) = 1.02-3.42]. No appreciable association was observed for total alcohol, whereas small inverse associations were observed for beer and wine, although confidence intervals were wide. An elevated lung-cancer risk was also observed for past liquor consumption (between ages 30 and 40 y). The adjusted OR for 1 or more drinks per day of liquor compared with infrequent drinkers was 1.83 (95% CI = 1. 06-3.15). Confounding of the association between alcohol and lung cancer by smoking was apparent. Although we devoted considerable efforts to adjusting for smoking in our analyses, residual confounding is still possible because smoking and alcohol are closely associated. In addition, case-control studies including this study should be viewed with caution because of possible selection bias. An increased risk of lung cancer might occur with moderate drinking of hard liquor but confirmation is required in larger studies.

Alcohol Drinking↗