By S. Kan. National University of Health Sciences. 2018.
Receptors Whereas in PD dopamine D2 receptors are up-regulated generic 5 mg buspar fast delivery anxiety worksheets for teens, 5-HT2A receptor at least in earlier stages of the disease generic buspar 10 mg otc anxiety games, receptors are not Cortex →/ NORADRENERGIC increased in DLB and in particular are not up-regulated as a Noradrenaline result of neuroleptic medication (60). In addition to striatal Striatum dopamine deficits, dopamine losses in cortical areas also Cortex ↓ occur (Table 91. MAO-B ↑ The significance of the serotoninergic, noradrenergic, 5-HT, 5-hydroxytryptamine; AChE, acetylcholinesterase; and neuropeptide (e. The clinical significance of some of the cho- aSummary of neurochemical findings, reviewed Perry et al. Chapter 91: Dementia with Lewy Bodies 1307 GENETICS AD at a similar stage of dementia. The polymorphism caus- ing the K allele in the gene for butyrylcholinesterase has Familial cases of DLB have been reported, although the been reported to be associated with AD, although this find- majority of cases appear to be sporadic. Following the dis- ing has not been replicated by others. In DLB, an increased covery of two separate missense mutations in the -sy- number of butyrylcholinesterase K homozygotes have been nuclein gene on chromosome 4 in a small number of fami- found. It has been suggested that this genotype may partly lies with pathologically confirmed early-onset PD, mutation explain the enhanced responsiveness to cholinesterase inhib- screening was undertaken in this gene in both familial and itors in DLB (73). Although abnormalities in butyrylcho- sporadic cases of DLB (61). These studies failed to reveal linesterase are evident in AD, including elevated enzymatic any nucleotide changes within the exons screened. Such an influence may be via so-called susceptibility genes. Be- CLINICAL–PATHOLOGIC RELATIONSHIPS cause DLB shares pathologic overlap with PD and AD, Cognitive and Neuropsychiatric susceptibility genes of interest for both conditions have been considered in candidate gene approaches. For PD and DLB, In DLB, a consistent gradient of LB density has been noted, allelic frequencies of the cytochrome P-450 gene CYP2D6 as follows: substantia nigra entorhinal cortex cingulate (debrisoquine-4-hydroxylase) have been examined. The re- gyrus insula frontal cortex hippocampus occipital sults of these studies have been conflicting. Paralimbic and neocortical LB densities are highly frequency of the CYP2D6*B allele has been reported in correlated with each other but not with nigral pathology, DLB (62), whereas another study found no association (63). One study of pathologic burden allele in AD and DLB despite an increased frequency in versus clinical severity examined correlations between two PD (64). The current balance of evidence suggests that the simple measures of cognitive ability and a range of lesion CYP2D6*B allele is not a major genetic determinant of counts and neurochemical measures in the midfrontal cor- DLB. Severity of dementia was significantly The 4 type of apolipoprotein E is significantly elevated correlated with LB density, plaque density, and severity of in both DLB and AD, with a concomitant reduction in the cholinergic deficit, but not with neurofibrillary tangle den- E 3 type of apolipoprotein. Interestingly, although the 4 sity or synaptophysin levels. In contrast, in AD cases, tangle allele was associated with an increased risk for the develop- density and synaptophysin levels were most highly corre- ment of DLB, it did not appear to affect the burden of lated with clinical severity. This suggests that the dementias pathology, measured by senile plaque and neurofibrillary of DLB and AD may have different pathologic but similar tangle density in the neocortex (65). Other studies have failed to find is associated with neuronal loss in the substantia nigra (66). Most recently, a significant difference has been reported Neurologic for the allelic distribution of a pentanucleotide repeat within the promoter region of the nitric oxide synthase gene Cell loss in the ventrolateral tier of the substantia nigra is (NOS2A) in a comparison of autopsy-proven DLB cases the dominant pathologic correlate for parkinsonism in both with controls (68). This is associated with gliosis and Lewy body brain as a physiologic neuronal mediator, but excessive pro- formation. Dopaminergic neurons in this area of the sub- duction of nitric oxide (e. The net effect of loss of the modu- sonism, it has been shown that inhibitors of nitric oxide lating effects of dopamine within the putamen is increased synthase may provide protective benefit in the treatment of neuronal activity in the globus pallidus (internal segment). Because output from the globus pallidus (internal segment) Associations between polymorphisms within the 2- is inhibitory to the ventrolateral thalamic nucleus, this leads macroglobulin, 1-antichymotrypsin, and presenilin 1 to excessive inhibition of thalamic activity and thus reduced genes and DLB have not been demonstrated (after account- feedback to the motor cortex. The perturbation in this loop, ing for apolipoprotein E 4 allele frequency) (70–72). Because the presynaptic lesion is similar in the two disorders, the answer As with any patient presenting with cognitive impairment, may therefore lie postsynaptically. Evidence to support this obtaining a full history and performing a mental and physi- notion comes from postmortem neurochemical studies cal examination are essential steps toward making a firm comparing dopaminergic activities in DLB with those in clinical diagnosis.
The role of environmental fac- sequently demonstrated that the rat protein homologue is tors was given additional weight by initial results of twin likewise expressed in nerve terminals (105) discount buspar 10 mg otc anxiety symptoms mimic ms. The diminished expression of the mutant allele in lymphoblas- human homologue of -synuclein was independently iden- toid cell lines buy cheap buspar 5mg on line anxiety quizlet, and they suggest that the parkinsonian pheno- tified by Ueda et al. These investigators also showed by fractionation studies that -synuclein appears to Parkin be loosely associated with synaptic vesicles, and this localiza- Mutations in the parkin gene were first identified in Japa- tion has been confirmed in rat brain by ultrastructural analy- nese families with a unique variant of parkinsonism (89). Jensen and his colleagues (82) have shown that - This form is inherited in an autosomal-recessive pattern, synuclein binds to vesicles via its amino-terminal region, and typically begins at an early age; in the series of 17 pa- and that it is carried with vesicles by the fast component tients studied by Ishikawa and Tsuji (72), the age ranged of axonal transport. Interestingly, the A30P mutation ap- from 9 to 43 years, with a mean of 28. Many of the clinical pears to abolish vesicle-binding activity. What specific physiologic role -synuclein and its homo- features of patients with autosomal-recessive juvenile par- logues may play as vesicle-binding proteins remains a mys- kinsonism (ARJP) closely resemble those of idiopathic PD: tery. George and co-investigators (46) independently identi- tremor at rest, rigidity, bradykinesia, postural instability, fied an avian homologue of -synuclein, synelfin, as a gene gait freezing, and marked improvement with levodopa. We have shown that -synuclein ARJP more often present with dystonia, show a marked mRNA and protein are upregulated in the SNpc following clinical improvement after sleep, and often show hyperre- early developmental striatal target lesion (85). In general, they do not show cognitive decline results in the induction of apoptotic death in some, but not or autonomic failure, and the course is slowly progressive. However, in The motor predominance of their clinical signs is in keeping this model -synuclein is not expressed in apoptotic pro- with the pathologic findings, which indicate neuronal loss files; it is exclusively upregulated in normal-appearing neu- restricted to neurons of the SNpc and the locus coeruleus rons, suggesting that it plays a role either in maintaining (146). Vila and co-workers (155) reached a simi- region, and a marker for this region, D6S305, was found lar conclusion in a model of chronic MPTP toxicity. Screening support of the possibility that -synuclein may play a role of complementary DNA (cDNA) libraries with a probe for in a plasticity response in these injury models is the observa- a putative exon, which was also deleted in this patient, led tion that -synuclein mRNA in SN is up-regulated during to the identification of a sequence encoding an open reading the first 4 postnatal weeks, a period of maximal differentia- frame for a 465amino acid protein (89). The deduced tion and synaptogenesis among DA neurons (85). What amino acid sequence of this protein contains a ubiquitin precise role -synuclein plays in the development of DA homology domain at the N-terminal, and a ring-finger neurons remains to be established. The gene encoding the protein is gous -synuclein null mice have thus far shown no obvious large [ 500 kilobase (kb)], and contains 12 exons. Deletion abnormalities in numbers or morphology of DA neurons; mutations were identified in four other affected patients density of striatal dopaminergic terminals; the number, in three independent families, confirming the pathogenetic morphology, or patch/matrix distribution of striatal neu- significance. These animals, however, do exhibit an in- pressed in various regions, including the SN (89). In addition, they show diminished behavioral activa- dividuals from 18 unrelated Japanese families revealed four tion following administration of amphetamine (4). The deletions affected exon has been a tendency to assume that the mutations cause a 3, exon 4, and exons 3 to 4, and a 1–base pair (bp) deletion toxic gain of function related to aggregation. It is important in exon 5resulted in a frameshift and an early stop. Further to keep in mind, however, that its function is unknown, and molecular analysis of non-Japanese families in Europe, re- that a loss of function may relate to disease pathogenesis. In vealed that in addition to deletion mutations, a variety of that regard, we have found that -synuclein mRNA levels point mutations resulting in either truncation or missense are diminished in the SNpc of patients with sporadic PD could also cause the phenotype (3). Markopoulou and colleagues (103) have shown in a identified patients with a late age of onset, up to 58 years 1786 Neuropsychopharmacology: The Fifth Generation of Progress in one case, and indicated that in some instances the clinical auto-oxidation of DA. This auto-oxidation generates toxic phenotype was indistinguishable from idiopathic PD (3). In addition, the pres- There is now growing recognition that mutations in par- ence of neuromelanin in the cell may alter the ability of kin may cause what clinically resembles idiopathic PD. In metal ions to participate in the production of reactive oxy- an investigation of the scope of the molecular and clinical gen species (145). Among early-onset patients without affected selectively destroy DA neurons—6-hydroxydopamine (6- family members, 18% had mutations. Many of the duce superoxide anion radical, H2O2, and hydroxyl radical. In all, 19 different rearrangements of exons mutations tions can be directed toward catecholamine neurons.
In primary amyloidosis the fibrils consist of monoclonal or or discount buspar 10mg mastercard anxiety 10 months postpartum, rarely 10mg buspar visa anxiety symptoms 50, fibrinogen or lysozyme in familial amyloidosis. In secondary amyloidosis the fibrils consist of protein A. O f the Senile, 2% (2) (5) 135 patients with am yloidosis, 83% had the prim ary form. Fam ilial, secondary, and senile Localized, 8% (11) am yloidosis accounted for less than 10% of patients. Localized am yloid is lim ited to the involved organ and never becom es system ic. In localized am yloidosis, the fibrils consist of an im m unoglobulin light chain; however, the patients do not have a m onoclonal protein in Primary (AL), 83% their serum or urine. M ost localized am yloidosis occurs in the respiratory tract, genitouri- (112) nary tract, or skin. From 1981 to 1992, of the 474 40 M edian age: 64 y (n=474) patients seen within 30 days of diagnosis the m edian age was 64 Age range: 32–90 y 37 years. O nly 1% were younger than 40 years, and m ales were affected m ore often than were fem ales. W eakness or fatigue and weight 52 loss were the m ost frequent initial sym ptom s seen within 30 days 50 of diagnosis. W eight loss occurred in m ore than half of patients. The m edian weight loss was 23 lb; five patients lost m ore than 40 100 lb each. Purpura, particularly in the periorbital and facial areas, was noted in about one sixth of patients. Gross bleeding was 30 reported initially in only 3%. Skeletal pain was a m ajor sym ptom 20 in only 5% and usually was related to lytic lesions or fractures 15 associated with m ultiple m yelom a. Dyspnea, pedal edem a, pares- 10 thesias, light-headedness, and syncope were noted. The external audito- ry canal may be occluded completely by nodules of amy- loid. This condition frequently produces deafness, which may be the initial symptom. M acroglossia occurs initially in about 10% of patients. Note the im print of the teeth on the dorsum of the tongue. This patient was unable to close his m outh and com plained of drooling. M acroglossia m ay cause obstruction of the airway, som etim es necessitating a tracheostom y. Infiltration of the periarticular tissues with amyloid may produce this sign. The shoulder pad sign causes pain and limitation of motion and is very difficult to treat. Despite the m uscular appearance, results of a biopsy revealed displace- m ent of m uscle fibers with am yloid. Patients often exhibit stiffness or lim itation of m ove- m ent. The liver was palpable in about one fourth 25 of patients seen within 30 days of diagnosis. Hepatomegaly is due to infiltration of amyloid or congestion from heart failure. The spleen is 20 palpable in only 5% of patients and rarely extends more than 5 cm below the left costal margin. Hemoglobin and platelet values within 30 days of diagnosis of primary systemic amyloidosis. Renal insufficiency was present in alm ost Anemia was not a prominent feature. W hen present, it usually is due to multiple myeloma, renal half of patients.
Transformed yeast cells containing noprecipitate the GABA-A receptor from cell extracts safe buspar 10 mg anxiety eating. In addition to known proteins that mediate and regulate Protein interactions suggested to occur by the yeast two- GPCR signaling (heterotrimeric G proteins buspar 10 mg with amex anxiety 7 minute test, GRKs, ar- hybrid system can be examined using various in vitro bio- restins), which were originally identified by functional as- chemical techniques, such as affinity chromatography facili- says using biochemical purification, cDNA cloning meth- tated by GST-fusion proteins. In addition to serving as an ods have facilitated the identification of additional protein independent assay for previously defined candidate interact- interactions with GPCRs that were completely unantici- ing proteins, this method can be used to identify novel pated (61). These novel protein interactions, while their protein interactions with GPCRs de novo (63). In this functional relevance remains unclear in many cases, are of method a DNA encoding a polypeptide sequence of interest great interest and potential therapeutic importance as drug is fused to GST using standard cDNA cloning techniques targets. The GST Of the many techniques for identifying novel pro- portion of the fusion protein allows the efficient immobili- tein–protein interactions developed over the last 10 years, zation of the protein by binding to agarose beads covalently interaction cloning methods such as the yeast two-hybrid derivatized with glutathione. Proteins from a cell or tissue system (62) have been particularly useful for studies of extract that bind to the fusion protein then can be isolated GPCRs. In the yeast two-hybrid system, protein interac- as an immobilized protein complex by affinity chromatogra- tions are detected by their ability to reconstitute the activity phy. A transcrip- shown recently (64) that the third cytoplasmic loop of the tion factor such as GAL4 can be divided into two domains: dopamine D2 receptor binds specifically to spinophilin, a a DNA binding domain and a transcriptional activation large cytoskeleton-associated protein that also binds to pro- domain. For the transcription factor to be active, these two tein phosphatase-1. A polypeptide sequence for which one phy using GST-fusion proteins. However, even in the event that extensive colocalization is observed, immunocytochem- ical techniques of this sort do not provide direct evidence for a physical interaction between candidate proteins. Coimmunoprecipitation techniques, as discussed above, A provide a useful method for addressing this question. How- ever, demonstrating that a specific protein association can occur in vivo is only the first step in the process of assessing the potential physiologic relevance of a novel protein inter- action, as this method generally does not provide any infor- mation regarding the possible functional activity of a candi- date protein interaction. Addressing this question can be a challenging task that involves creative application of diverse techniques and functional assays. Examples of novel protein interactions with GPCRs for which compelling functional data exist include the aforementioned interaction of the D2 dopamine receptor with ABP280 (65) and interaction of the 2-adrenergic receptor with NHERF/EBP50-family B proteins (51,63). Schematic diagram of G-protein–coupled receptor (GPCR) signaling. Following agonist binding, GPCRs activate heterotrimeric G proteins (G), which then regulate the activity of specific cellular effectors. Followingagonist binding,GPCRs canassoci- ate with members of diverse families of intracellular proteins, Unexpected Signaling, Cross-Talk, and including heterotrimeric G proteins (G), polyproline-binding pro- Transactivation Involving GPCRs teins such as those containing SH3 domains (SH3), arrestins (Arr), G-protein–coupled receptor kinases (GRK), small guanosine tri- (Fig. These Another line of evidence suggesting the existence of func- interactions allow GPCRs to initiate multiple intracellular signal- tionally relevant, novel protein interactions involving ing pathways, with each subtype of receptor likely coupled to GPCRs comes from recent work by several labs suggesting a relatively unique set of effectors. Heptahelical receptor signaling: beyond the G pro- that unanticipated functional interactions can occur be- tein paradigm. The RTK family includes the epidermal growth factor receptor (EGFR), the first receptor shown to have intrinsic tyrosine mechanism of cross-talk involves the formation of hetero- kinase activity (67,68). For tide growth factors (such as EGF) to the extracellular do- example, recent studies suggest that the nonreceptor tyro- main of the RTK, it has been observed recently that certain sine kinase c-Src can associate with the 2-adrenergic recep- GPCRs can initiate signaling cascades traditionally thought tor and the -arrestin in endocytic membranes, thus me- to be controlled by RTKs. For example, several GPCRs can by c-Src-mediated phosphorylation of co-endocytosed mediate transactivation of coexpressed EGFRs, thus stimu- EGFR (72). One Visualization of Protein Localization and mechanism of GPCR-mediated transactivation involves the Interaction in Living Cells activation of a membrane-associated metalloproteinase, which cleaves the EGF precursor protein to generate in- As discussed above, immunochemical methods are useful creased amounts of ligand for the EGFR (70). Another for examining the localization of proteins in intact cells. Indeed, we view newer molecular and because they require disruption of the cell membrane and cell biological approaches as complementing, rather than prolonged incubation of specimens with antibodies used to replacing, the sophisticated pharmacologic methods that detect the receptor of interest. The discovery of proteins have been developed over the years since the discovery of from certain marine animals that have high levels of intrinsic receptors as important drug targets.