Ca2+ promotes erythrocyte band 3 tyrosine phosphorylation via dissociation of phosphotyrosine phosphatase from band 3

Abstract

The anion-exchange band 3 protein is the main erythrocyte protein that is phosphorylated by protein tyrosine kinase (PTK). We have previously identified a band 3-associated phosphotyrosine phosphatase (PTP) that is normally highly active and prevents the accumulation of band 3 phosphotyrosine. Band 3 tyrosine phosphorylation can be induced by inhibition of PTP (vanadate, thiol oxidation), activation of PTK (hypertonic NaCl) or intracellular increased Ca(2+) (mechanism unknown). We now show that there is inhibition of dephosphorylation of band 3 in Ca(2+)/ionophore-treated erythrocytes and in membranes isolated from the treated cells. These membranes exhibit phosphatase activity upon the addition of exogenous substrate. Dephosphorylation of the endogenous substrate (band 3) can be activated in these membranes by the addition of Mg(2+). Thus the inability of PTP to dephosphorylate the band 3 phosphotyrosine is not due to inhibition of the enzyme itself. Ca(2+) rise in the erythrocyte causes dissociation of PTP from band 3, thus leaving the kinase unopposed. This is shown by a significant diminution in band 3/PTP co-precipitation. Addition of Mg(2+) to these membranes leads to reassociation of band 3 with PTP. The Ca(2+)-induced inhibition of band 3 dephosphorylation may be due to Ca(2+)-dependent alterations in membrane components and structure, affecting the interaction of band 3 with PTP. The Ca(2+)-induced tyrosine phosphorylation, involving an apparent PTP inhibition via dissociation from the substrate, may play a role in signal transduction pathways and in certain pathological disorders associated with increased cell Ca(2+).

Fibrinogen Effects of Erythrocyte Nitric Oxide Metabolism in Presence of Timolol

“…The activation of PKC increased ED as showed [26]. PKC phosphorylates PTK and protein tyrosine phosphatase (PTP) proteins promoting activation and inhibition of their enzyme activities respectively resulting in band 3 phosphorylation [27]. So, in erythrocytes MDL has double function to inhibit the adenylyl cyclase enzyme and be an indirect factor of band 3 protein phosphorylation.…”

Human kidney anion exchanger 1 localisation in MDCK cells is controlled by the phosphorylation status of two critical tyrosines

“…5). The lack of an effect of increasing calcium levels suggests that some aspects of tyrosine phosphorylation differ between eAE1 and kAE1, possibly because of an inability of the truncated kAE1 to interact with the phosphatase PTP-1B responsible for the calcium sensitivity of eAE1 (Zipser et al, 2002).…”

“…In addition to the results seen with pervanadate (Harrison et al, 1994), human eAE1 is phosphorylated in cells exposed to hypertonic medium (Minetti et al, 1996;Minetti et al, 1998) or calcium (Zipser et al, 2002). We tested a range of potential stimuli on MDCKIkAE1 cells for their effects on kAE1 phosphorylation.…”

Erythrocyte: Programmed Cell Death

“…This phosphatase is normally highly active and prevents the accumulation of band 3 phosphotyrosine. However, in A23187-treated erythrocytes increased intracellular Ca 2+ was found to promote band 3 tyrosine phosphorylation via dissociation of phosphotyrosine phosphatase from band 3 (Zipser et al, 2002). Tyrosine phosphorylation of band 3 markedly reduced its affinity for ankyrin, leading to release of band 3 from the spectrin/actin membrane skeleton, enhancement of the lateral mobility of band 3 in the bilayer, and progressive vesiculation.…”