Biomedical subjects

J W Patrick

Publications and source records attributed to J W Patrick.

At least 19 recordsLinked to original sources

PubMed2006

Role of sugars in regulating transfer cell development in cotyledons of developing Vicia faba seeds.

Transfer cell formation in cotyledons of developing faba bean (Vicia faba L.) seeds coincides with an abrupt change in seed apoplasm composition from one dominated by hexoses to one in which sucrose is the principal sugar. On the basis of these observations, we tested the hypothesis that sugars induce and/or sustain transfer cell development. To avoid confounding effects of in planta developmental programs, we exploited the finding that adaxial epidermal cells of cotyledons, which do not become transfer cells in planta, can be induced to form functional transfer cells when cotyledons are cultured on an agar medium. Growth rates of cotyledons cultured on hexose or sucrose media were used to inform choice of sugar concentrations. The same proportion of adaxial epidermal cells of excised cotyledons were induced to form wall ingrowths independent of sugar species and concentration supplied. In all cases, induction of wall ingrowths coincided with a marked increase in the intracellular sucrose-to-hexose ratio. In contrast, further progression of wall ingrowth deposition was correlated positively with intracellular sucrose concentrations that varied depending upon external sugar species and supply. Sucrose symporter induction and subsequent maintenance behaved identically to wall ingrowth formation in response to an external supply of hexoses or sucrose. However, in contrast to wall ingrowth formation, induction of sucrose symporter activity was delayed. We discuss the possibility of intracellular sugars functioning both as signals and substrates that induce and control subsequent development of transfer cells.

Carbohydrates↗

PubMed2004

Expression and localisation analysis of the wheat sucrose transporter TaSUT1 in vegetative tissues.

Previously we reported the isolation of three sucrose transporter genes, TaSUT1A, 1B and 1D, all expressed at high levels in the developing grains of hexaploid wheat ( Triticum aestivum L.), but also in a variety of other tissues. In order to further characterise the expression of the TaSUT1 genes in wheat plants, we have analysed TaSUT1 expression in their vegetative tissues using semi-quantitative reverse transcription-polymerase chain reaction, in situ hybridisation and immunolocalisation. The three TaSUT1 genes, which encode 98% identical SUT proteins, all appeared to be expressed at the same level in leaf blades, leaf sheaths and internodes, as well as developing grains, of hexaploid wheat. In mature leaf blades, TaSUT1 protein localised to the plasma membrane of phloem sieve elements in all classes of veins. In contrast, TaSUT1 mRNA was found to be localised to phloem companion cells. A similar localisation pattern for TaSUT1 protein was observed in veins of leaf sheaths and internodes. These results suggest that the wheat SUT1 has a transport function in enucleate sieve elements, in both veins responsible for loading photoassimilates, and in veins for axial transport. Furthermore, transport of the fluorescent dye carboxyfluorescein was used to investigate symplasmic connectivity between sieve element-companion cell complexes and non-phloem cells. Observations in source leaves indicated that sieve element-companion cell complexes of minor veins were symplasmically restricted, suggesting a role of TaSUT1 in apoplasmic phloem loading. In contrast, the dye was able to move symplasmically out of the phloem in internodes. In these circumstances TaSUT1 may also have a role in retrieving sucrose leaked to the phloem apoplasm.

Gene Expression↗

PubMed2001

Normal apoptosis levels in mice expressing one alpha7 nicotinic receptor null and one L250T mutant allele.

The alpha7 nicotinic receptor (nAChR) is a ligand-gated ion channel mediating cholinergic transmission throughout the nervous system. To further characterize the function of this receptor, we generated mice expressing the alpha7 L250T nAChR mutation and demonstrated that homozygous (T/T) L250T mice die within 24 h of birth and display extensive apoptosis and abnormal layering within their cortex. We now demonstrate that mice with one alpha7 null and one L250T allele (-/T) show little apoptosis and normal development of their cortex yet exhibit the same lethal phenotype as T/T mice. Furthermore, L250T mice show normal levels of apoptosis in other nervous system regions expressing alpha7 nAChRs. These results suggest that apoptosis is not the cause of death for L250T neonatal mice.

Alleles↗

PubMed2001

Compartmentation of transport and transfer events in developing seeds.

Developing seeds are net importers of organic and inorganic nutrients. Nutrients enter seeds through the maternal vascular system at relatively high concentrations in the phloem. They exit importing sieve elements via interconnecting plasmodesmata and, during subsequent symplasmic passage, are sequestered into labile storage pools (vacuoles; starch). Transporters function to retrieve nutrients leaked to the seed apoplasm during symplasmic passage. Maternal cells responsible for nutrient release to the seed apoplasm are characteristically located at the maternal/filial interface. Their plasma membranes are enriched in transport proteins and, in some species, these cells are modified to a transfer cell morphology. Apoplasmic volumes of seeds are relatively small, but contain high concentrations of sugars, potassium and a range of amino acids. Sucrose and amino acids are taken up from the seed apoplasm by one to two cell layers of filial tissues that juxtapose the maternal tissues. The plasma membranes of the uptake cells are enriched in sucrose and amino acid/H(+) transporters which co-localize with H(+)-ATPASES: In some species, these cells are modified to a transfer cell morphology. High densities of plasmodesmata support symplasmic delivery of accumulated nutrients to underlying storage cells where polymer formation (starch, protein) takes place. Hexoses, resulting from sucrose hydrolysis and leakage to the seed apoplasm, are retrieved by hexose/H(+) symporters.

Amino Acids↗

PubMed2000

Excess "read-through" acetylcholinesterase attenuates but the "synaptic" variant intensifies neurodeterioration correlates.

Acute stress increases the risk for neurodegeneration, but the molecular signals regulating the shift from transient stress responses to progressive disease are not yet known. The "read-through" variant of acetylcholinesterase (AChE-R) accumulates in the mammalian brain under acute stress. Therefore, markers of neurodeterioration were examined in transgenic mice overexpressing either AChE-R or the "synaptic" AChE variant, AChE-S. Several observations demonstrate that excess AChE-R attenuates, whereas AChE-S intensifies, neurodeterioration. In the somatosensory cortex, AChE-S transgenics, but not AChE-R or control FVB/N mice, displayed a high density of curled neuronal processes indicative of hyperexcitation. In the hippocampus, AChE-S and control mice, but not AChE-R transgenics, presented progressive accumulation of clustered, heat shock protein 70-immunopositive neuronal fragments and displayed a high incidence of reactive astrocytes. Our findings suggest that AChE-R serves as a modulator that may play a role in preventing the shift from transient, acute stress to progressive neurological disease.

Acetylcholinesterase↗

PubMed2000

Amino acid determinants of alpha 7 nicotinic acetylcholine receptor surface expression.

Transient transfection has not been a successful method to express the alpha7 nicotinic acetylcholine receptor such that these receptors are detected on the cell surface. This is not the case for all ligand-gated ion channels. Transient transfection with the 5-hydroxytryptamine type 3 subunit cDNA results in detectable surface receptor expression. Cell lines stably expressing the alpha7 nicotinic acetylcholine receptor produce detectable, albeit variable, levels of surface receptor expression. alpha7 nicotinic acetylcholine receptor surface expression is dependent, at least in part, on cell-specific factors. In addition to factors provided by the cells used for receptor expression, we hypothesize that the surface expression level in transfected cells is an intrinsic property of the receptor protein under study. Employing a set of alpha7-5-hydroxytryptamine type 3 chimeric receptor subunit cDNAs, we expressed these constructs in a transient transfection system and quantified surface receptor expression. We have identified amino acids that control receptor distribution between surface and intracellular pools; surface receptor expression can be manipulated without affecting the total number of receptors. These determinants function independently of the cell line used for expression and the transfection method employed. How these surface expression determinants in the alpha7 nicotinic acetylcholine receptor might influence synaptic efficacy is discussed.

Amino Acid Sequence↗

PubMed2000

Fast activation of a time-dependent outward current in protoplasts derived from coats of developing Phaseolus vulgaris seeds.

An outward current that appeared to activate instantaneously in response to depolarising voltage pulses at low sampling frequencies predominated in the plasma membrane of ground-parenchyma protoplasts derived from coats of developing Phaseolus vulgaris L. (cv. Redland Pioneer) seeds. However, the outward current showed time-dependent activation when higher sampling frequencies were used to measure the current. Activation of the current was best described as a double-exponential time course with the fast and slow time constants being 1 and 20 ms, respectively. The current also exhibited a rapid deactivation that followed a double-exponential time course with time constants of approximately 2 and 30 ms, respectively. "Tail-current" analysis allowed us to show that this current exhibited a low selectivity between K- and Cl- (PK:Cl = 1.8). Such a fast-activating current may account for some of the reports of time-independent, instantaneous currents that have been observed in plasma membranes of plant cells digitised at low sampling frequencies. Therefore, when "instantaneous" currents appear it is advisable to characterise these currents using higher sampling frequencies with correspondingly higher filtering frequency cut-offs.

Fabaceae↗

PubMed2000

Altered baroreflex responses in alpha7 deficient mice.

The autonomic nervous system controls and coordinates several cardiovascular functions, including heart rate, arterial pressure, blood flow and vasomotor tone. Neuronal nicotinic acetylcholine receptors (nAChRs) are the interface between the nervous system and the cardiovascular system, but it is not known which nAChR subtypes regulate autonomic function in vivo. Nicotinic AChRs containing the alpha7 subunit are a candidate subtype in autonomic ganglia. Stimulation of these nAChRs can increase neurotransmitter release via presynaptic mechanisms, as well as mediate fast synaptic transmission via postsynaptic mechanisms. To investigate the role of the alpha7 nAChR subunit in cardiac autonomic function, we measured baroreflex-mediated responses in alpha7 null mice. Here we show that the alpha7 null mice have impaired sympathetic responses to vasodilatation, as sodium nitroprusside infusion triggered a 48% heart rate increase in wild type mice but only a 21% increase in the alpha7 nulls (P < 0.001). The mutant mice developed supersensitivity to adrenergic agonists, although norepinephrine release from sympathetic nerve terminals could be elicited through mechanisms alternative to nAChR stimulation. Baroreflex-mediated parasympathetic responses were normal in alpha7 null mice. The decreased baroreflex-mediated tachycardia in alpha7 mutant mice indicates that alpha7-containing nAChRs participate in the autonomic reflex that maintains blood pressure homeostasis. The alpha7 mutant mice may serve as a model of baroreflex impairment arising from autonomic dysfunction.

Animals↗

PubMed2000

Hexose transporters of tomato: molecular cloning, expression analysis and functional characterization.

A full-length (LeHT2) and two partial (LeHT1 and LeHT3) cDNA clones, encoding hexose transporters, were isolated from tomato (Lycopersicon esculentum) fruit and flower cDNA libraries. Southern blot analysis confirmed the presence of a gene family of hexose transporters in tomato consisting of at least three members. The full-length cDNA (LeHT2) encodes a protein of 523 amino acids, with a calculated molecular mass of 57.6 kDa. The predicted protein has 12 putative membrane-spanning domains and belongs to the Major Facilitator Superfamily of membrane carriers. The three clones encode polypeptides that are homologous to other plant monosaccharide transporters and contain conserved amino acid motifs characteristic of this superfamily. Expression of the three genes in different organs of tomato was investigated by quantitative PCR. LeHT1 and LeHT3 are expressed predominantly in sink tissues, with both genes showing highest expression in young fruit and root tips. LeHT2 is expressed at relatively high levels in source leaves and certain sink tissues such as flowers. LeHT2 was functionally expressed in a hexose transport-deficient mutant (RE700A) of Saccharomyces cerevisiae. LeHT2-dependent transport of glucose in RE700A exhibited properties consistent with the operation of an energy-coupled transporter and probably a H+/hexose symporter. The Km of the symporter for glucose is 45 microM.

Amino Acid Sequence↗

PubMed2000

Mice homozygous for the L250T mutation in the alpha7 nicotinic acetylcholine receptor show increased neuronal apoptosis and die within 1 day of birth.

The alpha7 nicotinic acetylcholine receptor (nAChR) has been implicated in modulating neurotransmitter release and may play a role in the regulation of neuronal growth and differentiation. A threonine for leucine 247 substitution in the channel domain of the chick alpha7 nAChR increases agonist affinity and decreases the rate of desensitization, creating a "gain of function" model for this receptor. We have generated mice that express the analogous mutation (L250T) in the alpha7 nAChR using the techniques of homologous recombination and here report their characteristics. Mice heterozygous (+/T) for the L250T mutation are viable, fertile, and anatomically normal compared with wild-type littermates. In contrast, homozygous (T/T) L250T mice die within 2-24 h of birth. Brains of T/T mouse pups exhibit a marked reduction in alpha7 nAChR protein levels and show extensive apoptotic cell death throughout the somatosensory cortex. Furthermore, alpha7 L250T nAChRs are functionally expressed on neurons within the brains of T/T neonatal mice and have properties that are consistent with those observed for the rat alpha7 L250T and the chick alpha7 L247T mutant nAChRs expressed in oocytes. These findings indicate that neurons in the developing brain expressing only alpha7 L250T mutant nAChRs are susceptible to abnormal apoptosis, possibly due to increased Ca2+ influx.

Animals↗

PubMed2000

Effluxes of solutes from developing seed coats of Phaseolus vulgaris L. and Vicia faba l.: locating the effect of turgor in a coupled chemiosmotic system.

Cells lining the developing seed coats of legumes efflux photosynthates (mostly sucrose) and salts (mostly of potassium) into the apoplast for uptake by the developing embryo. These effluxes increase transiently in response to an increase in turgor in the effluxing cells. Detached coats of developing seed of P. haseolus vulgaris and Vicia faba were used to study the effects of turgor on the rates of efflux, on the membrane potential difference and on the membrane pH difference, using a number of inhibitors and agents which might affect signal cascades involving cytoplasmic calcium concentration. Effluxes were measured by measuring the concentrations of solutes of interest in solution samples placed in halves of detached seed coats, the paired halves serving as control and treated sample where appropriate. It is shown that a number of substances affect sucrose and potassium effluxes differently, and that hypo-osmotic shock depolarizes the efflux cells and acidifies the cytoplasm (in P. vulgaris). It is concluded that sucrose and potassium effluxes, although both are increased by an increase in turgor, are affected by different signal pathways. Further, it is also concluded that the signal that increases the rates of both sucrose efflux (via sucrose-proton antiport) and proton pump acts directly on the antiporter rather than on the pump. There are interesting parallels and contrasts between these processes and those in plants such as the charophyte Lamprothamnium after hypo-osmotic shock.

Calcium↗

PubMed2000

Amino acid transporters are localized to transfer cells of developing pea seeds.

To determine the nature and cellular localization of amino acid transport in pea seeds, two cDNA clones belonging to the AAP family of H(+)/amino acid co-transporters (PsAAP1 and PsAAP2) were isolated from a cotyledon cDNA library of pea (Pisum sativum L.). Functional expression in the yeast amino acid uptake mutants 22Delta6AAL and 22Delta8AA showed that PsAAP1 mediates transport of neutral, acidic, and basic amino acids. RNA-blot analyses showed that PsAAP1 is expressed in seeds and vegetative organs, including amino acid sinks and sources, whereas PsAAP2 could not be detected. For developing seeds, transcripts of PsAAP1 were detected in coats and cotyledons, with seed coats giving a weak signal. In cotyledons, expression was highest in epidermal-transfer-cell-enriched tissue. RNA in situ hybridization analysis showed that PsAAP1 was predominantly present in epidermal transfer cells forming the outer surface of cotyledons, which abuts the seed coats. Overall, our observations suggest that this transporter, which is localized in transfer cells of cotyledons, might play a role in the uptake of the full spectrum of amino acids released from seed coats.

Amino Acid Sequence↗

PubMed1999

Multiorgan autonomic dysfunction in mice lacking the beta2 and the beta4 subunits of neuronal nicotinic acetylcholine receptors.

Transcripts for the beta2 and the beta4 nicotinic acetylcholine receptor (nAChR) subunits are found throughout the CNS and the peripheral nervous system. These two beta subunits can form heteromultimeric channels with any of the alpha2, alpha3, alpha4, or alpha5 subunits in heterologous expression systems. Nonetheless, the subunit composition of native nAChRs and the role of different nAChR subtypes in vivo remain unclear. We prepared null mutations for the beta2 and the beta4 genes and bred beta2-/-beta4-/- mice by mating mice of identical beta2-/-beta4+/- or beta2+/-beta4-/- genotype. The beta2-/- and the beta4-/- single-mutant mice grow to adulthood with no visible phenotypic abnormalities. The beta2-/-beta4-/- double mutants survive to birth but have impaired growth and increased perinatal mortality. They also present enlarged bladders with dribbling urination and develop urinary infection and bladder stones. The ocular pupils are widely dilated and do not constrict in response to light. Histological studies revealed no significant abnormalities of brain or peripheral tissues except for hyperplasia in the bladder mucosa of beta4-/- and beta2-/-beta4-/- mutants. Bladder strips from beta2-/-beta4-/- mice did not respond to nicotine but contracted when stimulated with a muscarinic agonist or electric field stimulation. Bladder strips from beta4 mutants did not respond to nicotine despite the absence of major bladder dysfunction in vivo. Acetylcholine-activated whole-cell currents were absent in superior cervical ganglion neurons from beta2-/-beta4-/- mice and reduced in neurons from beta4-/- mice. Although there is apparent redundancy and a superficially normal phenotype in beta2-/- and beta4-/- mice, physiological studies indicate major deficits in the beta4-/- mice. Our previous description of a similar phenotype in alpha3-/- mice and the current data suggest that the alpha3 and the beta4 subunits are major components in autonomic nAChRs. The phenotype of the beta2-/-beta4-/- and alpha3-/- mice resembles the autosomal recessive megacystis-microcolon-hypoperistalsis syndrome in humans.

Animals↗

PubMed1999

Manipulations of ACHE gene expression suggest non-catalytic involvement of acetylcholinesterase in the functioning of mammalian photoreceptors but not in retinal degeneration.

To explore role(s) of acetylcholinesterase (AChE) in functioning and diseased photoreceptors, we studied normal (rd/+) and degenerating (rd/rd) murine retinas. All retinal neurons, expressed AChEmRNA throughout fetal development. AChE and c-Fos mRNAs peaked at post-natal days 10-12, when apoptosis of rd/rd photoreceptors begins. Moreover, c-Fos and AChEmRNA were co-overexpressed in rd/rd mice producing transgenic human (h), and host (m) AChE, but not in rd/+ mice. However, mAChE overexpression also occurred in transgenics expressing human serum albumin. Drastic variations in AChE catalytic activity were ineffective during development. Neither transgenic excess nor diisopropylfluorophosphonate (DFP) inhibition (80%) affected the rd phenotype; nor did DFP exposure induce photoreceptor degeneration or affect other key cholinergic proteins in rd/+ mice, unlike reports of adult mice and despite massive induction under DFP of c-Fos70 years). Therefore, the extreme retinal sensitivity to AChE modulation may reflect non-catalytic function(s) of AChE in adult photoreceptors. These findings exclude AChE as causing the rd phenotype, suggest that its primary function(s) in mammalian retinal development are non-catalytic ones and indicate special role(s) for the AChE protein in adult photoreceptors.

Acetylcholinesterase↗

PubMed1999

Distributions of nicotinic acetylcholine receptor alpha7 and beta2 subunits on cultured hippocampal neurons.

The hippocampus receives cholinergic afferents and expresses neuronal nicotinic acetylcholine receptors. In particular, the alpha7 and beta2 nicotinic subunits are highly expressed in the hippocampus. There has been controversy about the location, distribution and roles of neuronal nicotinic acetylcholine receptors [Role L. W. and Berg D. K. (1996) Neuron 16, 1077-1085; Wonnacott S. (1997) Trends Neurosci. 20, 92-98]. Using immunocytochemistry and patch-clamp techniques, we examined the density and distribution of nicotinic receptors on rat hippocampal neurons in primary tissue culture. The density and distribution of alpha7 subunits change with days in culture. Before 10 days in culture, alpha7 expression, monitored immunocytochemically, is low and nicotinic currents are small or absent. In older cultures, about two-thirds of the neurons express nicotinic currents, and alpha7 appears in small patches on the soma and out along the neuronal processes. These patches of alpha7 subunits on the surface of the neuronal processes often co-localize with the presynaptic marker, synaptotagmin. The other most common nicotinic subunit, beta2, stays confined mainly to the soma and proximal processes, and beta2 is distributed more uniformly and is not specifically localized at presynaptic areas. The two subunits, alpha7 and beta2, have different expression patterns on the surface of the cultured hippocampal neurons. Taken together with previous physiological studies, the results indicate that alpha7 subunits can be found at presynaptic terminals, and at these locations, these calcium-permeable channels may influence transmitter release.

Animals↗

PubMed1999

Sucrose transport into developing seeds of Pisum sativum L.

The anatomy of developing pea seeds is characterized by transfer cells present in both coats and cotyledons at the maternal/filial interface. To determine the nature and cellular localization of sucrose transporters in pea seeds, a full-length clone of a sucrose/H+ symporter (PsSUT1) was isolated from a cotyledon cDNA library. Northern blot analyses of different organs showed that PsSUT1 is expressed in non-seed tissues, including sucrose sinks and sources. Within developing seeds, transcripts of PsSUT1 and PsAHA1 genes were detected in all tissues, while transcripts of a sucrose binding protein (GmSBP) were confined to cotyledon epidermal transfer cells. Signal intensities of PsSUT1 and PsAHA1 transcripts and protein products were most pronounced in the thin-walled parenchyma cells of seed coats and epidermal transfer cells of cotyledons. For cotyledons, the highest transporter densities were localized to those portions of plasma membranes lining the wall ingrowth regions of epidermal transfer cells. Responses of [14C]sucrose influx to metabolic inhibitors indicated that proton-coupled sucrose transport was operative in both seed coats and cotyledons. Cotyledon epidermal transfer cells were shown to support the highest sucrose flux. Maximal transport activity was found to account for the sucrose flux differences between seed tissues. Intercellular movement of the symplasmic tracer, 5-(6)-carboxyfluorescein (CF), demonstrated that symplasmic pathways interconnect the vascular tissues to thin-walled parenchyma transfer cells of seed coats and, for cotyledons, epidermal transfer cells to storage parenchyma cells.

Biological Transport↗

PubMed1999

The metrics process: Baylor's development of a "report card" for faculty and departments.

In 1996, Baylor College of Medicine began the first year of its "metrics process," collecting, analyzing, and reporting data on the performance of each individual faculty member and each department in achieving the school's missions of education, patient care, research, service, and finance. This article is a report of the first two years of the process, with updates about the 1999 process, future plans, and lessons learned. The primary goal of the metrics process is to provide meaningful data to assess and improve the performance of faculty and departments across all missions. The authors (1) indicate the categories chosen, within each mission of the school, for measuring faculty time and effort (e.g., patient care, with or without learners) and state the measures chosen (e.g., percentage of time); (2) describe the development of questionnaires in 1996 and 1997 to acquire data from faculty, in the chosen categories and measures, about the time and effort they spent; and (3) report highlights of the resulting departmental data that were gathered in 1997. Among the key categories and units of measure chosen for measuring faculty (and departmental) time and effort are research grant dollars (total and per research full-time equivalent, or FTE); basic research grant dollars per square foot of laboratory space; percentage of faculty who spend at least 50% of their time in research who are National Institutes of Health principal investigators; numbers of inpatient and outpatient visits per evaluation and management FTE; total relative value units (RVUs) per patient-care FTE; patient-care income/RVU and expense/RVU for total faculty and support staff; percentage of faculty with at least one leadership position in a state or national organization; and income in excess of expense, by mission (e.g., patient care). Results of comparing data from the first two years of the metrics process demonstrate marked improvements in performance for most research measures (i.e., items of measurement agreed upon for the metrics process). The process is continually being redeveloped; the ultimate challenge is to place the objective measurements in a context where less objective qualities (e.g., innovation) also figure importantly in the evaluation and fostering of excellence. The metrics process is providing important management data, encouraging significant discussions among faculty and chairs about performance and accountability, and aiding greatly in departmental goal-setting and ultimately in determining the overall performance of the school.

Evaluation Studies as Topic↗

PubMed1998

Contributions of N-linked glycosylation to the expression of a functional alpha7-nicotinic receptor in Xenopus oocytes.

The alpha7 subunit of the neuronal nicotinic acetylcholine receptor, when expressed in Xenopus oocytes, forms homooligomeric ligand-gated ion channels that are blocked by a snake toxin, alpha-bungarotoxin. The amino-terminal extracellular domain of the alpha7 sequence has three consensus sites for asparagine-linked glycosylation (N46DS, N90MS, and N133AS). In this study, we show that alpha7 expressed either in vivo or in vitro is a glycoprotein of 57 kDa. In addition, we demonstrate by site-directed mutagenesis that all three consensus sites are used for glycosylation. To elucidate the role(s) of asparagine-linked glycosylation in the formation and function of the alpha7 receptor, wild-type and glycosylation-deficient alpha7 subunits were expressed in COS cells and oocytes. We examined biochemical and physiological properties of expressed receptors and found that alpha7 glycosylation mutations do not affect homooligomerization and surface protein expression of the alpha7 receptor but do affect surface expression of alpha-bungarotoxin binding sites and the function of the receptor. Our data indicate that asparagine-linked glycosylation is required for the expression of a functional alpha7 receptor in oocytes.

Amino Acid Sequence↗