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M V Prasad

Publications and source records attributed to M V Prasad.

8 recordsLinked to original sources
PubMed1995

Activation of Jun kinase/stress-activated protein kinase by GTPase-deficient mutants of G alpha 12 and G alpha 13.

Signal transduction pathways regulated by G12 and G13 heterotrimeric G proteins are largely unknown. Expression of activated, GTPase-deficient mutants of alpha 12 and alpha 13 alter physiological responses such as Na+/H+ exchanger activity, but the effector pathways controlling these responses have not been defined. We have found that the expression of GTPase-deficient mutants of alpha 12 (alpha 12Q229L) or alpha 13 (alpha 13Q226L) leads to robust activation of the Jun kinase/stress-activated protein kinase (JNK/SAPK) pathway. Inducible alpha 12Q229L and alpha 13Q226L expression vectors stably transfected in NIH 3T3 cells demonstrated JNK/SAPK activation but not extracellular response/mitogen-activated protein kinase activation. Transient transfection of alpha 12Q229L and alpha 13Q226L also activated the JNK/SAPK pathway in COS-1 cells. Expression of the GTPase-deficient mutant of alpha q (alpha qQ209L) but not alpha i (alpha iQ205L) or alpha s (alpha sQ227L) was also able to activate the JNK/SAPK pathway. Functional Ras signaling was required for alpha 12Q229L and alpha 13Q226L activation of the JNK/SAPK pathway; expression of competitive inhibitory N17Ras inhibited JNK/SAPK activation in response to both alpha 12Q229L and alpha 13Q226L. The results describe for the first time a Ras-dependent signal transduction pathway involving JNK/SAPK regulated by alpha 12 and alpha 13.

3T3 Cells↗
PubMed1994

Protein kinase C-dependent and -independent activation of Na+/H+ exchanger by G alpha 12 class of G proteins.

Constitutively activated mutants of the G alpha 12 class of G proteins, G alpha 12(Q229L) and G alpha 13(Q226L), were transiently expressed in COS-1 cells, and the activity of amiloride-sensitive Na+/H+ exchanger was measured. The expression of either G alpha 12(Q229L) or G alpha 13(Q226L) increased the basal activity of the amiloride-sensitive exchanger by 2-5-fold. Regulation of this activation by other G protein signaling pathways was investigated by the transient expression of constitutively activated G protein mutants of G alpha s(Q227L), G alpha i2(Q205L), and G alpha q(Q209L) in COS-1 cells. Only G alpha q showed a similar activation of the exchanger. Chronic treatment of the transfected cells with 4 beta-phorbol 12-myristate 13-acetate to deplete the endogenous protein kinase C completely inhibited the activation of the antiporter by G alpha 12(Q229L), whereas activation by G alpha 13(Q226L) remained unaffected. These results indicated that both G alpha 12 and G alpha 13 can activate Na+/H+ exchanger by two distinct signaling pathways. G alpha 12 activation of the exchanger was dependent on protein kinase C pathway, whereas G alpha 13 activation was not. These studies define the involvement of G alpha 12 class of G proteins, for which no function has been assigned yet, in the activation of Na+/H+ exchanger.

Amiloride↗
PubMed1994

A simple non-distillation method for the estimation of Ru-106 in urine.

A simple method has been developed for estimating Ru-106 in urine. Urine samples spiked with 3-50 Bq of Ru-106 and 200 micrograms of ruthenium carrier were initially oxidized using an HNO3-H2O2 mixture. Attempts to recover ruthenium by various preconcentration methods after the initial oxidation resulted in recoveries ranging from 10-54% depending on the experimental conditions. For near quantitative recoveries, the organic matter in urine was completely destroyed by wet ashing with HNO3-H2O2 (method A) or HNO3-H2O2 followed by H2SO4 treatment (method B). The ruthenium was oxidized to RuO4 using potassium periodate and allowed to react in situ with polyethylene powder. The polyethylene powder was separated, washed and its beta activity was counted. The recovery of ruthenium was 86.9 +/- 4.6% (RSD 5.3%) in method A; and 94.4 +/- 2.6% (RSD 2.8%) in method B. The minimum detection limit achieved was 0.59 Bq/dm3. Interferences due to Cs-137 and Sr-90 were studied.

Humans↗
PubMed1993

Retinoblastoma gene inhibits transactivation of HIV-LTR linked gene expression upon co-transfection in He La cells.

Co-transfection of HeLa cells with plasmids carrying human immunodeficiency virus (HIV) control elements along with plasmids harboring human retinoblastoma (RB) gene, results in the repression of transactivation of genes linked to HIV elements. Cells transfected with HIV LTR-linked chloramphenicol acetyl transferase (CAT) and TAT genes showed a dose-dependent decrease in CAT activity when increasing amounts of RB genes were transfected along with HIV genes. CAT mRNAs were not detected in HeLa cells transfected with HIV LTR CAT gene alone. Upon cotransfection of these cells with pTAT gene, large quantities of CAT messengers were observed. The TAT gene mediated expression of CAT gene was inhibited when cells were co-transfected with RB gene. These studies suggest that the RB gene represses HIV LTR directed CAT gene expression by interfering with the expression of HIV TAT gene.

Chloramphenicol O-Acetyltransferase↗
PubMed1992

Simultaneous spectrophotometric estimation of thorium and calcium in urine.

A simple and rapid method for the simultaneous estimation of thorium and calcium in urine was developed. Thorium and calcium were coprecipitated as oxalates at pH 3-4 and were determined using Thoronol as reagent. A multi-wave-length linear regression analysis procedure was applied. Thorium recovery was found to be 78.3% +/- 5.1% (1 sigma) and that of calcium was 93.7 +/- 3.0% (1 sigma). The minimum detection limit for thorium was found to be 2.54 mBq/dm3. The analytical results of calcium agree very well with those determined by EDTA titrimetry.

Calcium↗
PubMedDate not supplied

G protein subunits and cell proliferation.

Heterotrimeric, guanine nucleotide binding proteins, known as G proteins, provide signaling mechanisms for the serpentine family of receptors. Recent studies indicate that the alpha- as well as the beta gamma-subunits of the G proteins are involved in the regulation of several cellular responses. Some of these responses proved to be critical for the regulation of cell growth and differentiation. Studies using the constitutively activated mutants of the G alpha subunits and the overexpression of G beta gamma subunits have indicated that these different subunits regulate cell proliferation through diverse signaling pathways involving distinct low molecular weight GTPases and specific protein kinases. The integrated networking between these different pathways finally defines the coordinated regulation of cell proliferation. This review briefly summarizes our present understanding of the different signaling mechanisms involved in the regulation of cell proliferation by the different G alpha and G beta gamma subunits.

Animals↗
PubMedDate not supplied

Frusemide-induced bullous pemphigoid.

Bullous pemphigoid is a rare complication of frusemide therapy. We present two patients in whom the link between frusemide and this condition was not recognised early, and continued frusemide therapy resulted in prolonged leg blistering and ulceration. On withdrawing the drug, all lesions in both patients resolved completely. Although uncommon, this frusemide reaction needs to be borne in mind as it can add to the morbidity of elderly patients with heart failure.

Aged↗