Prevalence of enteropathogens in cats with and without diarrhea in four different management models for unowned cats in the southeast United States.

The objective of this study was to determine the prevalence of enteropathogens in cats with and without diarrhea in four different models for managing unowned cats: short-term animal shelter, long-term sanctuary, home-based foster care, and trap-neuter-return. Fecal samples from 482 cats, approximately half of the cats with normal fecal consistency and half with diarrhea, were tested by zinc sulfate centrifugation and by real-time PCR for a panel of enteropathogens. At least one enteropathogen of feline or zoonotic importance was detected in a majority of cats, regardless of management model. For most enteropathogens, the presence or absence of diarrhea was not significantly associated with infection, the exceptions being Tritrichomonas foetus in sanctuary cats with diarrhea (26%) and normal fecal consistency (10%), respectively (P≤0.04), and feline coronavirus in foster cats (80% and 58%) (P≤0.001). The types of enteropathogens detected were related to the type of management model, e.g., viral and protozoal infections were most common in shelters, sanctuaries, and foster homes (confinement systems), whereas helminth infections were most common in trap-neuter-return programs (free-roaming cats). These results suggest that management practices for unowned cats are inadequate for control of enteropathogens and that the presence of diarrhea is a poor indicator of enteropathogen carriage. Risk-management strategies to reduce transmission to people and other animals should focus on sanitation, housing, compliance with preventive care guidelines, periodic surveillance, response to specific enteropathogens, humane population management of free-roaming community cats, public health education, and minimizing the duration and number of cats in mass confinement.

Rapid Diagnosis of Babesia gibsoni by Point-of-Need Testing by Insulated Isothermal PCR in Dogs at High Risk of Infection.

BACKGROUND: Dogs seized by law enforcement agencies during dogfighting investigations are at increased risk of Babesia gibsoni infection. A rapid and cost-effective diagnostic test would increase the feasibility of mass screening of dogs for infection and monitoring treatment efficacy in B. gibsoni-infected dogs. OBJECTIVE: To determine the performance of a point-of-need insulated isothermal PCR (iiPCR) test for diagnosis of B. gibsoni in dogs rescued in dogfighting investigations. ANIMALS: Two hundred and thirty-three dogs seized in dogfighting investigations. METHODS: Cross-sectional study. Whole blood samples were tested for B. gibsoni and Babesia spp. by iiPCR. Results were compared to a reference standard comprised of concordant results from real-time PCR in a commercial diagnostic laboratory and antibody titers. RESULTS: The iiPCR system was quick to learn, portable, and had a short processing time of <2 hours. Sensitivity and specificity of the iiPCR assay for B. gibsoni were 90% (95% confidence interval [CI] 81-95%) and 99% (CI, 95-100%), respectively. Sensitivity and specificity of the iiPCR assay for Babesia spp. were 87% (CI, 78-93%) and 98% (CI, 0.94-99%), respectively. CONCLUSIONS AND CLINICAL IMPORTANCE: The iiPCR system produced few false-positive results, indicating that positive results are likely to represent true infections when used in high-risk animals. The iiPCR system can fail to identify 10-15% of truly infected dogs. However, the portability, speed, and economy of the iiPCR system compared to testing through a reference laboratory can allow rescue groups to screen and identify infection in more dogs.

Perioperative mortality in cats and dogs undergoing spay or castration at a high-volume clinic.

High volume spay-neuter (spay-castration) clinics have been established to improve population control of cats and dogs to reduce the number of animals admitted to and euthanazed in animal shelters. The rise in the number of spay-neuter clinics in the USA has been accompanied by concern about the quality of animal care provided in high volume facilities, which focus on minimally invasive, time saving techniques, high throughput and simultaneous management of multiple animals under various stages of anesthesia. The aim of this study was to determine perioperative mortality for cats and dogs in a high volume spay-neuter clinic in the USA. Electronic medical records and a written mortality log were used to collect data for 71,557 cats and 42,349 dogs undergoing spay-neuter surgery from 2010 to 2016 at a single high volume clinic in Florida. Perioperative mortality was defined as deaths occurring in the 24h period starting with the administration of the first sedation or anesthetic drugs. Perioperative mortality was reported for 34 cats and four dogs for an overall mortality of 3.3 animals/10,000 surgeries (0.03%). The risk of mortality was more than twice as high for females (0.05%) as for males (0.02%) (P=0.008) and five times as high for cats (0.05%) as for dogs (0.009%) (P=0.0007). High volume spay-neuter surgery was associated with a lower mortality rate than that previously reported in low volume clinics, approaching that achieved in human surgery. This is likely to be due to the young, healthy population of dogs and cats, and the continuous refinement of techniques based on experience and the skills and proficiency of teams that specialize in a limited spectrum of procedures.

Performance of 4 Point-of-Care Screening Tests for Feline Leukemia Virus and Feline Immunodeficiency Virus.

BACKGROUND: More than 3 million cats in the United States are infected with FeLV or FIV. The cornerstone of control is identification and segregation of infected cats. HYPOTHESIS/OBJECTIVES: To compare test performance with well-characterized clinical samples of currently available FeLV antigen/FIV antibody combination test kits. ANIMALS: Surplus serum and plasma from diagnostic samples submitted by animal shelters, diagnostic laboratories, veterinary clinics, and cat research colonies. None of the cats had been vaccinated against FIV. The final sample set included 146 FeLV+, 154 FeLV-, 94 FIV+, and 97 FIV- samples. METHODS: Prospective, blind comparison to a gold standard: Samples were evaluated in 4 different point-of-care tests by ELISA antigen plate tests (FeLV) and virus isolation (FIV) as the reference standards. All test results were visually read by 2 blinded observers. RESULTS: Sensitivity and specificity, respectively, for FeLV were SNAP® (100%/100%), WITNESS® (89.0%/95.5%), Anigen® (91.8%/95.5%), and VetScan® (85.6%/85.7%). Sensitivity and specificity for FIV were SNAP® (97.9%/99.0%), WITNESS® (94.7%/100%), Anigen® (96.8%/99.0%), and VetScan® (91.5%/99.0%). CONCLUSIONS AND CLINICAL IMPORTANCE: The SNAP® test had the best performance for FeLV, but there were no significant differences for FIV. In typical cat populations with seroprevalence of 1-5%, a majority of positive results reported by most point-of-care test devices would be false-positives. This could result in unnecessary segregation or even euthanasia.

Prevalence of upper respiratory pathogens in four management models for unowned cats in the Southeast United States.

Upper respiratory infection (URI) is a pervasive problem in cats and impacts the capacity and cost of sheltering programs. This study determined the pattern of respiratory pathogens in cats with and without clinical signs of URI in four different models for managing unowned cats, namely, (1) short-term animal shelters (STS), (2) long-term sanctuaries (LTS), (3) home-based foster care programs (FCP), and (4) trap-neuter-return programs for community cats (TNR). Conjunctival and oropharyngeal swabs from 543 cats, approximately half of which showed clinical signs of URI, were tested for feline herpes virus-1 (FHV), feline calicivirus (FCV), Chlamydia felis, Bordetella bronchiseptica, Mycoplasma felis, and canine influenza virus by real-time PCR. FHV (59%, 41%) and B. bronchiseptica (33%, 24%) were more prevalent in both clinically affected and nonclinical cats, respectively, in STS than other management models. FCV (67%, 51%) and M. felis (84%, 86%) were more prevalent in LTS than any other management model. Clinically affected cats in FCP were more likely to carry FHV (23%, 6%), C. felis (24%, 10%), or M. felis (58%, 38%) than were nonclinical cats. Clinically affected cats in TNR were more likely to carry FCV (55%, 36%) or C. felis (23%, 4%) than were nonclinical cats. The prevalence of individual pathogens varied between different management models, but the majority of the cats in each model carried one or more respiratory pathogens regardless of clinical signs. Both confined and free-roaming cats are at risk of developing infectious respiratory disease and their health should be protected by strategic vaccination, appropriate antibiotic therapy, effective biosecurity, feline stress mitigation, and alternatives to high-density confinement.

A novel KCNA1 mutation identified in an Italian family affected by episodic ataxia type 1.

Episodic ataxia type 1 (EA1) is a rare human neurological syndrome characterized by continuous myokymia and attacks of generalized ataxia that can be triggered by abrupt movements, emotional stress and fatigue. An Italian family has been identified where related members displayed continuous myokymia, episodes of ataxia, attacks characterized by myokymia only, and neuromyotonia. A novel missense mutation (F414C), in the C-terminal region of the K(+) channel Kv1.1, was identified in the affected individuals. The mutant homotetrameric channels were non-functional in Xenopus laevis oocytes. In addition, heteromeric channels resulting from the co-expression of wild-type Kv1.1 and Kv1.1(F414C), or wild-type Kv1.2 and Kv1.1(F414C) subunits displayed reduced current amplitudes and altered gating properties. This indicates that the pathogenic effect of this KCNA1 mutation is likely to be related to the defective functional properties we have identified.

Infectious diseases of dogs and cats on Isabela Island, Galapagos.

BACKGROUND: Vaccination and importation of dogs and cats are prohibited in the Galapagos, resulting in a uniquely isolated population. The purpose of this study was to determine the prevalence of infectious diseases of dogs and cats that impact their health, could spill over to native wildlife, or sentinel diseases of concern to humans. HYPOTHESIS: The isolation of dogs and cats in the Galapagos protects them from diseases common in mainland populations. ANIMALS: Ninety-five dogs and 52 cats presented during a neutering campaign. METHODS: A prospective cross-sectional study was performed. Blood was collected for serological and DNA evaluation of a panel of infectious diseases. RESULTS: Antibodies against parvovirus (100%), parainfluenza virus (100%), adenovirus 1/2 (66-67%), and distemper virus (22%) were present in dogs. Dirofilaria immitis was also common in dogs (34%), with lower prevalences of Wolbachia pipiens (22%), Bartonella sp. (13%), Ehrlichia/Anaplasma spp. (1%), and Mycoplasma haemocanis (1%) observed. Antibodies against panleukopenia virus (67%), Toxoplasma gondii (63%), calicivirus (44%), and herpesvirus 1 (10%) were detected in cats. Feline leukemia virus antigen, feline immunodeficiency virus antibody, or coronavirus antibodies were not detected. Bartonella sp. (44%) infections were common in cats, but only one was infected with M. haemofelis. CONCLUSIONS AND CLINICAL IMPORTANCE: Despite their relative seclusion from the rest of the world, cats and dogs of Isabela were exposed to many pathogens found in mainland South America. Parasite prophylaxis, neutering, and strict enforcement of animal movement restrictions would control a majority of the diseases. In the absence of vaccination, a reservoir of susceptible animals remains vulnerable to new disease introductions.

Experimental transmission of a herpesvirus in Greek tortoises (Testudo graeca).

An experimental transmission study aimed at fulfilling Koch's postulates for a herpesvirus-associated stomatitis-rhinitis in Mediterranean tortoises is presented. Clinical, pathologic, serologic, and molecular studies were performed linking tortoise herpesvirus with the pathogenesis of stomatitis-rhinitis. Four adult Greek tortoises received either intranasally or intramuscularly two tortoise herpesvirus isolates by primary experimental infection and secondary challenge 11 months later. After the primary experimental infection and the secondary challenge, clinical signs of illness developed, which included conjunctivitis, diphtheritic oral plaques, and oral discharge. At 4 weeks after the secondary challenge, all tortoises were humanely euthanatized and evaluated. Although neutralizing antibodies developed after the primary experimental infection, they apparently did not prevent the later development of recurrent clinical signs. Polymerase chain reaction (PCR) and reverse transcription-PCR analyses allowed sensitive characterization of the systemic distribution of the herpesvirus DNA sequences and their presence in the cranial nerves and brains of the infected tortoises. Despite the failure to recover the herpesviruses used in the transmission study, the findings support the premise that tortoise herpes-virus is a primary pathogen of Greek tortoises.

Application of immunoperoxidase-based techniques to detect herpesvirus infection in tortoises.

Indirect (IIP) and direct (DIP) immunoperoxidase assays were developed for the serological and histological diagnoses of herpesvirus infection in tortoises, respectively. A mouse monoclonal antibody (MAb HL1546), specific for the heavy chain of tortoise IgY, was used as the secondary antibody in the IIP assay. Rabbit polyclonal antisera raised against 2 sucrose gradient-purified tortoise herpesvirus isolates (HV4295/7R/95 and HV1976) were used as primary antibodies for the detection of herpesvirus antigen either in infected cell cultures or in formalin-fixed, paraffin-embedded tissues. The IIP and DIP assays could detect either the presence of anti-herpesvirus antibody in the plasma of exposed tortoises or the presence of herpesvirus antigen in infected tissues, respectively. Although the IIP test complements the enzyme-linked immunosorbent assay and the serum neutralization test already available for measuring herpesvirus-specific antibody in tortoises, the DIP test is useful for the histological diagnosis of herpesvirus infection in tortoises.

Multiple sites of interaction between the intracellular domains of an inwardly rectifying potassium channel, Kir6.2.

The amino-terminal and carboxy-terminal domains of inwardly rectifying potassium channel (Kir) subunits are both intracellular. A direct physical interaction between these two domains is involved in the response of Kir channels to regulatory factors such as G-proteins, nucleotides and intracellular pH. We have previously mapped the region within the N-terminal domain of Kir6.2 that interacts with the C-terminus. In this study we use a similar in vitro protein-protein interaction assay to map the regions within the C-terminus which interact with the N-terminus. We find that multiple interaction domains exist within the C-terminus: CID1 (amino acids (aa) 279-323), CID2 (aa 214-222) and CID3 (aa 170-204). These domains correlate with regions previously identified as making important contributions to Kir channel assembly and function. The highly conserved nature of the C-terminus suggests that a similar association with the N-terminus may be a feature common to all members of the Kir family of potassium channels, and that it may be involved in gating of Kir channels by intracellular ligands.

Enzyme-linked immunosorbent assay for detecting herpesvirus exposure in Mediterranean tortoises (spur-thighed tortoise [Testudo graeca] and Hermann's tortoise [Testudo hermanni]).

An enzyme-linked immunosorbent assay (ELISA) was developed for the detection of antibodies to a herpesvirus associated with an upper respiratory tract disease in Mediterranean tortoises [spur-thighed tortoise (Testudo graeca) and Hermann's tortoise (Testudo hermanni)]. This serodiagnostic test was validated through a hyperimmunization study. The mean of the A(405) readings of the plasma samples collected at time zero of the hyperimmunization study plus three times the standard deviation was used as the cutoff for seropositivity in tortoises. ELISA results were compared to serum neutralization (SN) values for the same samples by using the McNemar test. The results obtained by SN and ELISA were not significantly different (P > 0.05). This new ELISA could be used as an important diagnostic tool for screening wild populations and private and zoo collections of Mediterranean tortoises.

Differential pH sensitivity of Kir4.1 and Kir4.2 potassium channels and their modulation by heteropolymerisation with Kir5.1.

1. The inwardly rectifying potassium channel Kir5.1 appears to form functional channels only by coexpression with either Kir4.1 or Kir4.2. Kir4.1-Kir5.1 heteromeric channels have been shown to exist in vivo in renal tubular epithelia. However, Kir5.1 is expressed in many other tissues where Kir4.1 is not found. Using Kir5.1-specific antibodies we have localised Kir5.1 expression in the pancreas, a tissue where Kir4.2 is also highly expressed. 2. Heteromeric Kir5.1-Kir4.1 channels are significantly more sensitive to intracellular acidification than Kir4.1 currents. We demonstrate that this increased sensitivity is primarily due to modulation of the intrinsic Kir4.1 pH sensitivity by Kir5.1. 3. Kir4.2 was found to be significantly more pH sensitive (pK(a) = 7.1) than Kir4.1 (pK(a) = 5.99) due to an additional pH-sensing mechanism involving the C-terminus. As a result, coexpression with Kir5.1 does not cause a major shift in the pH sensitivity of the heteromeric Kir4.2-Kir5.1 channel. 4. Cell-attached single channel analysis of Kir4.2 revealed a channel with a high open probability (P(o) > 0.9) and single channel conductance of approximately 25 pS, whilst coexpression with Kir5.1 produced novel bursting channels (P(o) < 0.3) and a principal conductance of approximately 54 pS with several subconductance states. 5. These results indicate that Kir5.1 may form heteromeric channels with Kir4.2 in tissues where Kir4.1 is not expressed (e.g. pancreas) and that these novel channels are likely to be regulated by changes in intracellular pH. In addition, the extreme pH sensitivity of Kir4.2 has implications for the role of this subunit as a homotetrameric channel.

Treatment of localized prostate cancer with intermittent triple androgen blockade: preliminary results in 110 consecutive patients.

OBJECTIVES: To determine the effectiveness of triple androgen blockade as an alternative to watchful waiting, radical prostatectomy or radiation therapy in the management of patients with clinical stage T1 to T3 prostate cancer. METHODS: The records of 110 consecutive patients were retrospectively evaluated. Patients were treated with a three-drug androgen blockade regimen, consisting of a luteinizing hormone-releasing hormone agonist (leuprolide or goserelin) plus an antiandrogen (flutamide or bicalutamide) plus finasteride (a 5-alpha-reductase inhibitor), followed by finasteride maintenance therapy, as the sole intervention. All patients refused local therapy and had their prostates intact. Determinants of efficacy included serum prostate-specific antigen (PSA) levels and disease-specific survival. RESULTS: Patients were treated for a median of 13 months with triple androgen blockade. At baseline, mean PSA level was 13.2 +/- 1.2 ng/ml (range, 0.39-100 ng/ml), and mean Gleason score was 6.6 +/- 0.1 (range, 4-10). During treatment, PSA levels declined to < or =0.1 ng/ml in all patients, with a median time of 3 months. After a median follow-up of 36 months since initiation of treatment, PSA levels have remained stable in 105 of 110 patients (95.5%). At a median follow-up of 55 months (range, 38-125 months), the mean PSA level for the first 57 patients treated in this series is 1.88 +/- 0.1 (range, 0-11.0 ng/ml). Only 9 of 110 (8.1%) patients have a PSA level > or =4.0 ng/ml. To date, no patient has received a second cycle of hormone blockade. CONCLUSIONS: Although median follow-up is short, triple androgen blockade therapy followed by finasteride maintenance appears to be a promising alternative for the management of patients with clinically localized or locally advanced prostate cancer. Further study of this approach is warranted.

Partial characterization of retroviruses from boid snakes with inclusion body disease.

OBJECTIVE: To characterize retroviruses isolated from boid snakes with inclusion body disease (IBD). ANIMALS: 2 boa constrictors with IBD and 1 boa exposed to an affected snake. PROCEDURE: Snakes were euthanatized, and tissue specimens and blood samples were submitted for virus isolation. Tissue specimens were cultured with or without commercially available viper heart cells and examined by use of transmission electron microscopy (TEM) for evidence of viral replication. Reverse transcriptase activ ty was determined in sucrose gradient-purified virus. Western blotting was performed, using polyclonal antibodies against 1 of the isolated viruses. Specificity of the rabbit anti-virus antibody was evaluated, using an immunogold-labeling TEM technique. RESULTS: 3 viruses (RV-1, RV-2, and RV-3) were isolated. The isolates were morphologically comparable to members of the Retroviridae family. Reverse transcriptase activity was high in sucrose gradient fractions that were rich in virus. Polyclonal antibody against RV-1 reacted with proteins of similar relative mobility in RV-1 and RV-2. By use of immunogold labeling, this antibody also recognized virions of both RV-1 and RV-2. CONCLUSIONS AND CLINICAL RELEVANCE: A retrovirus was isolated from boid snakes with IBD or exposed to IBD. Western blot analysis of viral proteins indicated that viruses isolated from the different snakes were similar. Whether this virus represents the causative agent of IBD is yet to be determined. The isolation of retroviruses from boid snakes with IBD is an important step n the process of identifying the causative agent of this disease.

Unmodified calcium concentrations in tumour necrosis factor receptor subtype-mediated apoptotic cell death.

Tumour necrosis factor-alpha (TNF) receptors mediate a variety of effects dependent on cell type. A role for Ca2+ in TNF-induced death remains uncertain. Here we investigated restricting intracellular/extracellular Ca2+ in HeLa epithelial carcinoma cells expressing low and high levels of p75TNFR receptor subtype and KYM-1 rhabdomyosarcoma cells, models of rapid TNF-induced apoptosis. Ca2+ -chelators EGTA and BAPTA-AM as well as microsomal Ca2+ -ATPase inhibitor thapsigargin, did not alter TNF-induced death. TNF was also unable to alter resting [Ca2+]i levels which remained < 200 nM even during times when these cells were undergoing apoptotic cell death. These findings indicate no role for modulated Ca2+ concentrations in TNF-induced apoptotic cell death.

A novel method for measurement of submembrane ATP concentration.

There has been considerable debate as to whether adenosine triphosphate (ATP) is compartmentalized within cells and, in particular, whether the ATP concentration directly beneath the plasma membrane, experienced by membrane proteins, is the same as that of the bulk cytoplasm. This issue has been difficult to address because there is no indicator of cytosolic ATP, such as those available for Ca(2+), capable of resolving the submembrane ATP concentration ([ATP](sm)) in real time within a single cell. We show here that mutant ATP-sensitive K(+) channels can be used to measure [ATP](sm) by comparing the increase in current amplitude on patch excision with the ATP dose-response curve. In Xenopus oocytes, [ATP](sm) was 4.6 +/- 0.3 mm (n = 29) under resting conditions, slightly higher than that measured for the bulk cytoplasm (2.3 mm). In mammalian (COSm6) cells, [ATP](sm) was slightly lower and averaged 1.4 +/- 0.1 mm (n = 66). Metabolic poisoning (10 min of 3 mm azide) produced a significant fall in [ATP](sm) in both types of cells: to 1.2 +/- 0.1 mm (n = 24) in oocytes and 0.8 +/- 0.11 mm for COSm6 cells. We conclude that [ATP](sm) lies in the low millimolar range and that there is no gradient between bulk cytosolic and submembrane [ATP].

Direct photoaffinity labeling of Kir6.2 by [gamma-(32)P]ATP-[gamma]4-azidoanilide.

ATP-sensitive potassium (K(ATP)) channels are under complex regulation by intracellular ATP and ADP. The potentiatory effect of MgADP is conferred by the sulfonylurea receptor subunit of the channel, SUR, whereas the inhibitory effect of ATP appears to be mediated via the pore-forming subunit, Kir6.2. We have previously reported that Kir6.2 can be directly labeled by 8-azido-[gamma-(32)P]ATP. However, the binding affinity of 8-azido-ATP to Kir6.2 was low probably due to modification at 8' position of adenine. Here we demonstrate that Kir6.2 can be directly photoaffinity labeled with higher affinity by [gamma-(32)P]ATP-[gamma]4-azidoanilide ([gamma-(32)P]ATP-AA), containing an unmodified adenine ring. Photoaffinity labeling of Kir6.2 by [gamma-(32)P]ATP-AA is not affected by the presence of Mg(2+), consistent with Mg(2+)-independent ATP inhibition of K(ATP) channels. Interestingly, SUR1, which can be strongly and specifically photoaffinity labeled by 8-azido-ATP, was not photoaffinity labeled by ATP-AA. These results identify key differences in the structure of the nucleotide binding sites on SUR1 and Kir6.2.

pH dependence of the inwardly rectifying potassium channel, Kir5.1, and localization in renal tubular epithelia.

The physiological role of the inwardly rectifying potassium channel, Kir5.1, is poorly understood, as is the molecular identity of many renal potassium channels. In this study we have used Kir5.1-specific antibodies to reveal abundant expression of Kir5.1 in renal tubular epithelial cells, where Kir4.1 is also expressed. Moreover, we also show that Kir5.1/Kir4.1 heteromeric channel activity is extremely sensitive to inhibition by intracellular acidification and that this novel property is conferred predominantly by the Kir5.1 subunit. These findings suggest that Kir5.1/Kir4.1 heteromeric channels are likely to exist in vivo and implicate an important and novel functional role for the Kir5.1 subunit.

Role of receptor protein tyrosine phosphatase alpha (RPTPalpha) and tyrosine phosphorylation in the serotonergic inhibition of voltage-dependent potassium channels.

The activity of voltage-gated potassium (Kv) channels can be dynamically modulated by several events, including neurotransmitter-stimulated biochemical cascades mediated by G-protein-coupled receptors. By using a heterologous expression system, we show that activating the 5-HT2C receptor inhibits both Kv1.1 and Kv1.2 channels through a tyrosine phosphorylation mechanism. The major molecular determinants of channel inhibition were identified as two tyrosine residues located in the N-terminal region of the Kv channel subunit. Furthermore, we demonstrate that receptor protein tyrosine phosphatase alpha (RPTPalpha), a receptor protein tyrosine phosphatase, co-ordinates the inhibition process mediated via 5-HT2C receptors. We therefore propose that the serotonergic regulation of human Kv1.1 and Kv1.2 channel activity by the 5-HT2C receptor involves the dual coordination of both RPTPalpha and specific tyrosine kinases coupled to this receptor.

Mapping of the physical interaction between the intracellular domains of an inwardly rectifying potassium channel, Kir6.2.

The amino-terminal and carboxyl-terminal domains of inwardly rectifying potassium (Kir) channel subunits are both intracellular. There is increasing evidence that both of these domains are required for the regulation of Kir channels by agents such as G-proteins and nucleotides. Kir6.2 is the pore-forming subunit of the ATP-sensitive K(+) (K(ATP)) channel. Using an in vitro protein-protein interaction assay, we demonstrate that the two intracellular domains of Kir6.2 physically interact with each other, and we map a region within the N terminus that is responsible for this interaction. "Cross-talk" through this interaction may explain how mutations in either the N or C terminus can influence the intrinsic ATP-sensitivity of Kir6.2. Interestingly, the "interaction domain" is highly conserved throughout the superfamily of Kir channels. The N-terminal interaction domain of Kir6.2 can also interact with the C terminus of both Kir6.1 and Kir2.1. Furthermore, a mutation within the conserved region of the N-terminal interaction domain, which disrupts its interaction with the C terminus, severely compromised the ability of both Kir6.2 and Kir2.1 to form functional channels, suggesting that this interaction may be a feature common to all members of the Kir family of potassium channels.