Disease relevance of Xoom

• Purified oocyte membrane preparations from X. laevis oocytes previously microinjected with C6-2B rat astrocytoma mRNA, and subsequently defolliculated, exhibited novel beta AR and forskolin-stimulated adenylate cyclase activity [1].
• However, the inhibitory effect of progesterone was unaffected by pertussis toxin, even though the oocyte membrane Ni was fully ADP-ribosylated with pertussis toxin, as revealed by lack of further [32P]ADP-ribosylation on subsequent re-incubation with pertussis toxin [2].
• Both the photoaffinity bumetanide analogue, 4-[3H]benzoyl-5-sulfamoyl-3-(3-thenyloxy)benzoic acid, and an antiserum raised against Ehrlich ascites cell cotransporter specifically labeled an approximately 140-kDa oocyte membrane protein [3].

High impact information on Xoom

• Acetylcholine receptors in the oocyte membrane [4].
• Here, we use an identification strategy that is based on detergent solubilization of frog oocyte membrane proteins, followed by liposome reconstitution and evaluation by patch-clamp [5].
• When RNA transcripts are injected after fertilization, VSV G is expressed only in the internal cleavage membranes (basolateral orientation) and is excluded from the outer surface (apical orientation, original oocyte membrane) [6].
• Oogenic prolactin was secreted only into the blastocoel (from the cleavage membrane), none could be detected in the external medium (from the original oocyte membrane) [6].
• Injection into Xenopus oocytes, of RNA synthesized from this clone in vitro, results in expression of functional nicotinic receptors in the oocyte membrane [7].

Biological context of Xoom

• Although Xoom is actively transcribed during oogenesis, distribution and function of its translation product have not yet been clarified [8].
• Thereafter, localized expression of Xoom was observed in neural crest cells of the neural tube stage embryo and in optic and otic vesicles of tadpole [9].
• These results suggest that maternally expressed and membrane-associated Xoom is closely involved in the gastrulation movement through a lithium-inducible signal pathway [9].
• Overexpression and misexpression of Xoom induced overproduction of Xoom protein, but not a changed phenotype [10].
• The EC50 for stimulation of in vivo phosphodiesterase activity by insulin correlated with the IC50 for inhibition of oocyte membrane adenylate cyclase activity measured in vitro (2 and 4 nM, respectively) [11].

Anatomical context of Xoom

• Expression of Xoom maternally occurred in the whole oocyte at the early stage of oogenesis and the transcript was gradually localized in the animal hemisphere of full-grown oocytes [9].
• Two forms of Xoom protein were ubiquitously detected from unfertilized egg to tadpole stage, with a qualitative peak during blastula and gastrula stages [8].
• These results suggest that Xoom plays an important role in the epibolic movement of ectodermal cells through some regulation of actin filament organization [10].
• Membranes isolated from the temporal neocortex of a patient, operated for intractable epilepsy, were injected into oocytes and, within a few hours, the oocyte membrane acquired functional neurotransmitter receptors to gamma-aminobutyric acid, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, kainate, and glycine [12].
• These data prove the functional identity of the cloned HepG2 and adipocyte cDNAs and indicate that the HepG2 and adipocyte transporters display similar kinetic behavior when expressed in the frog oocyte membrane as compared with their native membrane environments [13].

Associations of Xoom with chemical compounds

• In examining a relation between Xoom and the dorsoventral patterning, lithium-treatment at 32-cell stage embryo decreased Xoom mRNA level within an hour, but coinjection of lithium with myo-inositol reversed the decreasing Xoom mRNA to normal level [9].
• After injection into Xenopus oocytes one mRNA fraction induced the appearance of chloride channels in the oocyte membrane [14].
• These results suggest that serotonin activation of receptors that are inserted into the oocyte membrane following injection of rat brain poly(A)+ mRNA can induce calcium release from intracellular stores [15].
• Membrane vesicles from Torpedo electroplaques were injected into the oocytes and, within a few hours, the oocyte membrane acquired AcChoRs and Cl- channels [16].
• RNA was size-fractionated on a sucrose gradient and a high-molecular-weight fraction (7-10 kilobase) encoding the alpha-subunit gave rise to functional voltage-dependent Na channels in the oocyte membrane [17].

Analytical, diagnostic and therapeutic context of Xoom

• Immunoblotting of oocyte membrane extracts treated with PNGase F indicates that NBCe1 is normally glycosylated at N597 and N617 (both on the third extracellular loop) [18].
• 4. Immunohistochemistry on cryosections confined the functionally active 1-3 plus 4-8 combination to the oocyte membrane [19].
• RESULTS: Chick retinal membrane fragments were efficiently grafted onto Xenopus oocytes after microinjection, with 22.9% +/- 7.6% of the oocyte membrane being stained with anti-chick retina antibody [20].
• Using the voltage-clamp technique to identify the mechanism underlying the ROS-measured effects, we found that RB induced a large increase in the oocyte membrane conductance (G(m)) [21].
• Accounting for the low rate of functional transplantation of nAChRs is their backward orientation in the oocyte membrane, since about 80% of them adopted an out-side-in orientation [22].

References