J Biol Chem, Vol. 274, Issue 29, 20165-20170, July 16, 1999

The Inhibition of Capacitative Calcium Entry Due to ATP Depletion but Not Due to Glucosamine Is Reversed by Staurosporine

From the Department of Cell Biology, The University of Alabama at Birmingham, Birmingham, Alabama 35294-0005

The capacitative Ca²⁺ entry pathway in J774 macrophages is rapidly inhibited by the amino sugar glucosamine. This pathway is also inhibited by treatments such as 2-deoxy-D-glucose (2dGlc) or glucose deprivation that inhibit glycolysis and lead to significant decreases in cellular ATP and other trinucleotides. We sought to determine whether glucosamine's effect on capacitative Ca²⁺ entry was also due to ATP depletion, as has been suggested recently for its link to insulin resistance. In contrast to brief treatments with 2dGlc, there was no significant decrease in ATP following exposure to glucosamine. In addition, the 2dGlc-mediated inhibition of capacitative Ca²⁺ influx was reversed by staurosporine, a microbial alkaloid that inhibits a broad range of protein kinases. Staurosporine was also able to reverse the inhibition of capacitative Ca²⁺ entry seen following other treatments that decreased cellular ATP levels, including cytochalasin B and iodoacetic acid. Other inhibitors of protein kinase C, including bisindolylmaleimide, K252a, H-7, and calphostin C, were unable to mimic this effect of staurosporine. However, the inhibition of capacitative Ca²⁺ influx in the presence of glucosamine was not reversed by staurosporine. These data indicate that the inhibitory action on capacitative Ca²⁺ entry of glucosamine is distinct from that caused by ATP depletion.