The regulation of Na, K-ATPase by PLMS, the phospholemman-like protein from shark. Molecular cloning, sequence, expression, cellular distribution and functional effects of PLMS

In Na,K-ATPase membrane preparations from shark rectal glands, we have previously identified an FXYD domain-containing protein, phospholemman-like protein from shark, PLMS. This protein was shown to associate and modulate shark Na,K-ATPase activity in vitro. Here we describe the complete coding sequence, expression, and cellular localization of PLMS in the rectal gland of the shark Squalus acanthias. The mature protein contained 74 amino acids, including the N-terminal FXYD motif and a C-terminal protein kinase multisite phosphorylation motif. The sequence is preceded by a 20 amino acid candidate cleavable signal sequence. Immunogold labeling of the Na,K-ATPase α-subunit and PLMS showed the presence of α and PLMS in the basolateral membranes of the rectal gland cells and suggested their partial colocalization. Furthermore, through controlled proteolysis, the C terminus of PLMS containing the protein kinase phosphorylation domain can be specifically cleaved. Removal of this domain resulted in stimulation of maximal Na,K-ATPase activity, as well as several partial reactions. Both the E1∼P → E2-P reaction, which is partially rate-limiting in shark, and the K+ deocclusion reaction, E2(K) → E1, are accelerated. The latter may explain the finding that the apparent Na+ affinity was increased by the specific C-terminal PLMS truncation. Thus, these data are consistent with a model where interaction of the phosphorylation domain of PLMS with the Na,K-ATPase α-subunit is important for the modulation of shark Na,K-ATPase activity

Effects of target location and uncertainty on reaching movements in standing position Los efectos de la ubicación de la diana y la incertidumbre en los movimientos de alcance en la posición vertical Efeitos da localização do alvo e da incerteza em movimentos de alcance na postura ereta

The effects of target location and uncertainty of target position on reaching movements while standing were investigated. Ten healthy, right-handed adults stood facing a 17'' touchscreen. They were instructed to press with their right index fingertip a push bottom and touch the center of the target displayed on the screen after it was lighted on, moving quickly their arm. The target was shown either ipsi- or contralateral to the right arm and either in a certain or uncertain position. Reaction time (RT), movement time (MT), and radial error (RE) were assessed. Results revealed shorter RT (&#8776; 35 ms) and smaller RE (&#8776; 0.19 cm) for certain than for uncertain condition and slightly longer RT (&#8776; 8 ms) and MT (&#8776; 18 ms) for reaches towards the contralateral target. In conclusion, the findings of this study showing the effect of uncertainty of target location as well as target position are also applied to arm reaching in standing position.<br>Los efectos de la ubicación de la diana y la incertidumbre acerca de la posición de la diana en los movimientos de alcance fueron investigados. Diez adultos sanos y diestros estaban frente a una pantalla táctil de 17''. Se les instruyó para presionar un interruptor con el dedo índice derecho y tocar el centro de la diana que aparece en la pantalla después de haber sido iluminado, moviéndo rápidamente su miembro superior. La diana fue mostrada ya sea ipsi o contralateralmente y los participantes tenían o no certidumbre sobre la posición de la misma. El tiempo de reacción (TR), el tiempo de movimiento (TM), y el error radial (ER) fueron evaluados. Los resultados revelaron ser más cortos TR (&#8776; 35 ms) y RE menor (&#8776; 0,19cm) en la condición de certeza y mayores TR (&#8776; 8 ms) y TM (&#8776; 18 ms) en los movimientos hacia la meta contralateral. En conclusión, los hallazgos de este estudio que muestra los efectos de la incertidumbre de la ubicación de la diana, así como la posición de la diana se aplican también a movimientos de alcance en la posición erecta.<br>Os efeitos da localização do alvo e da incerteza quanto à posição do alvo em movimentos de alcance foram investigados. Dez adultos permaneceram em pé em frente a um monitor sensível ao toque. Eles foram instruídos a pressionar com o dedo indicador direito um interruptor e tocar o centro do alvo apresentado no monitor após ele acender, movendo o membro superior rapidamente. O alvo foi mostrado ipsi ou contralateralmente e os participantes tinham ou não certeza sobre a posição do alvo. O tempo de reação (TR) e movimento (TM) e o erro radial (ER) foram avaliados. Os resultados revelaram menor TR (&#8776;35 ms) e ER (&#8776;0,19 cm) para a condição de certeza e maiores TR (&#8776;8 ms) e TM (&#8776;18 ms) para os moimentos ao alvo contralateral. Concluindo, esses achados mostraram que os efeitos da incerteza da localização e a posição final do alvo podem ser aplicados para movimentos de alcance na posição ereta