Functional Requirements for a Samd14-Capping Protein Complex in Stress Erythropoiesis

Abstract

Acute anemia induces rapid expansion of erythroid precursors and accelerated differentiation to replenish erythrocytes. Paracrine signals - involving cooperation between SCF/c-Kit signaling and other signaling inputs - are required for the increased erythroid precursor activity in anemia. Our prior work revealed that the Sterile Alpha Motif (SAM) Domain 14 (Samd14) gene increases the regenerative capacity of the erythroid system and promotes stress-dependent c-Kit signaling. However, the mechanism underlying Samd14s role in stress erythropoiesis is unknown. We identified a protein- protein interaction between Samd14 and the - and {beta} heterodimers of the F-actin capping protein (CP) complex. Knockdown of the CP {beta} subunit increased erythroid maturation in ex vivo cultures and decreased colony forming potential of stress erythroid precursors. In a genetic complementation assay for Samd14 activity, our results revealed that the Samd14-CP interaction is a determinant of erythroid precursor cell levels and function. Samd14-CP promotes SCF/c-kit signaling in CD71med spleen erythroid precursors. Given the roles of c-Kit signaling in hematopoiesis and Samd14 in c-Kit pathway activation, this mechanism may have pathological implications in acute/chronic anemia.