Expression of T Lymphocyte p56lck, a Zinc-Finger Signal Transduction Protein, Is Elevated By Dietary Zinc Deficiency and Diet Restriction in Mice

Compromised immune function is common to Zn deficiency, protein and energy malnutrition; however, the causative mechanisms at the molecular level have not been elucidated. The T lymphocyte signal transduction pathway contains several Zn-finger proteins, and it is possible that the in vivo functioning of these proteins could be affected by dietary deficiency of Zn and amino acids. Thus, the objective was to investigate the effects, on expression of the T lymphocyte signal transduction proteins p56(lck), phospholipase Cgamma1 (PLCgamma1) and protein kinase C (PKCalpha), of dietary Zn deficiency (ZnDF, < 1 mg Zn/kg diet) and protein-energy malnutrition syndromes [2% protein deficiency (LP), combined Zn and 2% protein deficiency (ZnDF+LP), and diet restriction (DR, body weight equal to ZnDF)] compared with control (C) mice. Indices of nutritional status and splenocyte counts were also determined. Based on serum albumin and liver lipid concentrations, the ZnDF+LP and LP groups had protein-type malnutrition, whereas the ZnDF and DR groups had energy-type malnutrition. For Western immunoblotting of the signal transduction proteins, mouse splenic T lymphocytes were isolated by immunocolumns. The expression of T lymphocyte p56(lck) was significantly elevated in the ZnDF+LP, ZnDF and DR groups compared to the C group. In contrast, the expression of PLCgamma1 and PKC was unaffected. There was a significant negative correlation between T lymphocyte p56(lck) expression and serum Zn (r= -0.65, P = 0.0007) or femur Zn (r = -0.73, P = 0.0001) concentrations. We propose that elevated T lymphocyte p56(lck) may contribute to altered thymoctye maturation, apoptosis and lymphopenia in Zn deficiency and protein-energy malnutrition syndromes.