Agonist-induced Internalization of the Caenorhabditis elegans Muscarinic Acetylcholine Receptor GAR-3 in Chinese Hamster Ovary Cells

The C. elegans VIG-1 and FRM-1 modulate carbachol-stimulated ERK1/2 activation in chinese hamster ovary cells expressing the muscarinic acetylcholine receptor GAR-3

Many neurotransmitter receptors are known to interact with a variety of intracellular proteins that modulate signaling processes. In an effort to understand the molecular mechanism by which acetylcholine (ACh) signaling is modulated, we searched for proteins that interact with GAR-3, the Caenorhabditis elegans homolog of muscarinic ACh receptors. We isolated two proteins, VIG-1 and FRM-1, in a yeast two-hybrid screen of a C. elegans cDNA library using the third intracellular (i3) loop of GAR-3 as bait. To test whether these proteins regulate ACh signaling, we utilized Chinese hamster ovary (CHO) cells stably expressing GAR-3 (GAR-3/CHO cells). Previously we have shown that the cholinergic agonist carbachol stimulates extracellular signal-regulated kinases 1 and 2 (ERK1/2) activation in an atropine-sensitive manner in this cell line. When VIG-1 was transiently expressed in GAR-3/CHO cells, carbachol-stimulated ERK1/2 activation was substantially reduced. In contrast, transient expression of FRM-1 significantly enhanced carbachol-stimulated ERK1/2 activation. Neither VIG-1 nor FRM-1 expression appeared to alter the affinity between GAR-3 and carbachol. In support of this notion, expression of these proteins did not affect GAR-3-mediated phospholipase C activation. To verify the modulation of ERK1/2 activity by VIG-1 and FRM-1, we used an i3 loop deletion mutant of GAR-3 (termed GAR-3Δi3). Carbachol treatment evoked robust ERK1/2 activation in CHO cells stably expressing the deletion mutant (GAR-3Δi3/CHO cells). However, transient expression of either VIG-1 or FRM-1 had little effect on carbachol-stimulated ERK1/2 activation in GAR-3Δi3/CHO cells. Taken together, these results indicate that VIG-1 and FRM-1 regulate GAR-3-mediated ERK1/2 activation by interacting with the i3 loop of GAR-3.

Cholinergic involvement and synaptic dynamin 1 expression in Yokukansan-mediated improvement of spatial memory in a rat model of early Alzheimer's disease

The aim of this study was to investigate the effect of Yokukansan (YKS) on the impairment of spatial memory and cholinergic involvement in a rat model of early-phase Alzheimer's disease (AD). In this model, rats underwent four-vessel transient cerebral ischemia and then were treated with beta amyloid oligomers injected intracerebroventricularly once daily for 7 days. These animals showed memory impairment in an eight-arm radial maze task without histological evidence of apoptosis but with a decrease in expression of hippocampal dynamin 1, an important factor in synaptic vesicle endocytosis. Oral administration of YKS for 2 weeks significantly increased the number of correct choices and decreased the number of error choices in the eight-arm radial maze task (P < 0.05). Moreover, YKS significantly increased high K⁺-evoked potentiation of acetylcholine (ACh) release (P < 0.05) and significantly increased the expression of dynamin 1 (P < 0.01) in the hippocampus. The ameliorative effect of YKS on spatial memory impairment in our rat model of early-phase AD may be mediated in part by an increase in ACh release and modulation of dynamin 1 expression, leading to improved synaptic function. Future studies will determine whether YKS is similarly useful in the treatment of memory defects in patients diagnosed with early-stage AD.

An isoimmune response to human sperm clathrin in an infertile woman with systemic lupus erythematosus

We have employed a proteomic approach to study the immune response to human sperm in an infertile female patient suffering from systemic lupus erythematosus (SLE). Human sperm antigenic extracts were resolved by means of two-dimensional electrophoresis and electroblotted onto nitrocellulose membranes. The membranes were incubated with serum from the SLE patient. Sperm antigens that were reactive to polyclonal antibodies were next visualized on X-ray film, using the enhanced chemiluminescence (ECL). Three spots corresponding to the positions of sperm immunoreactive antigens on a nitrocellulose membrane were localized in a silver stained gel and subjected to mass spectrometry. A database search of the sequences recognized by the analyzed SLE serum revealed its homology to the clathrin heavy chain (CHC). Further analysis revealed that anti-CHC antibody reacted with multiple sperm antigenic determinants, resolved by either one- or two-dimensional electrophoresis. When studied by immunofluorescence, we demonstrated anti-CHC antibody reactivity with the sperm tail tip (corresponding to the sperm agglutination pattern), also with the principal piece and with cytoplasmic droplets around the sperm midpiece. Live sperm clearly exhibited reactivity with the midpiece. This study demonstrates clathrin heavy chain on human sperm using serum of an infertile individual with a concomitant autoimmune disease.