Regulation of Alr1 Mg Transporter Activity by Intracellular Magnesium

Mg homeostasis is critical to eukaryotic cells, but the contribution of Mg transporter activity to homeostasis is not fully understood. In yeast, Mg uptake is primarily mediated by the Alr1 transporter, which also allows low affinity uptake of other divalent cations such as Ni2+, Mn2+, Zn2+ and Co2+. Using Ni2+ uptake to assay Alr1 activity, we observed approximately nine-fold more activity under Mg-deficient conditions. The mnr2 mutation, which is thought to block release of vacuolar Mg stores, was associated with increased Alr1 activity, suggesting Alr1 was regulated by intracellular Mg supply. Consistent with a previous report of the regulation of Alr1 expression by Mg supply, Mg deficiency and the mnr2 mutation both increased the accumulation of a carboxy-terminal epitope-tagged version of the Alr1 protein (Alr1-HA). However, Mg supply had little effect on ALR1 promoter activity or mRNA levels. In addition, while Mg deficiency caused a seven-fold increase in Alr1-HA accumulation, the N-terminally tagged and untagged Alr1 proteins increased less than two-fold. These observations argue that the Mg-dependent accumulation of the C-terminal epitope-tagged protein was primarily an artifact of its modification. Plasma membrane localization of YFP-tagged Alr1 was also unaffected by Mg supply, indicating that a change in Alr1 location did not explain the increased activity we observed. We conclude that variation in Alr1 protein accumulation or location does not make a substantial contribution to its regulation by Mg supply, suggesting Alr1 activity is directly regulated via as yet unknown mechanisms

Public Health Rep

The McLaughlin Public Health Service clinic serves several thousand Lakota people (Sioux) on Standing Rock Indian Reservation, SD. In 1981, a priority-setting exercise established for the first time a grassroots expression of the concerns of the clinic's staff. A three-step process was used in which each staff member first compiled an open-ended list of health needs, then ranked the relative contribution of five factors to making these problems important, and assessed each problem listed by those factors. The factors used were mortality, morbidity, vulnerability to intervention, facilities on hand, and social implications. The resulting priority table represented each person's assessment of the health needs of the community. A composite table was created to represent the group's assessment. The staff concluded that among the many problems listed, alcoholism and diabetes were the most compelling health problems. The priority score was almost identical for each, but the reasons were different. Alcoholism was rated highly because it was felt to be widespread and had serious social implications. Diabetes was ranked highly because it was felt to be lethal and vulnerable to intervention. A significant long-term benefit to the clinic of the 3-month process was to stimulate consultation within the local clinic and to unify the health team, endowing the members with a common sense of purpose.1987IHS000012-06/HS/AHRQ HHS/United States3112845PMCnull650