Common and ubiquitous in eukaryotic cells enables

Info icon This preview shows pages 17–21. Sign up to view the full content.

View Full Document Right Arrow Icon
Common and ubiquitous in eukaryotic cells Enables efflux of Ca2+ against its concentration gradient Found at both PM and ER (but different genes encode the 2 subcellularly distinct pumps) ER: SERCA pump (sarcoendoplasmic reticulum Ca2+-ATPase-dependent pump; has its own antagonists etc. PM: pump is controlled, in part, by Ca2+-calmodulin (thus, turned on by rapid increases in Ca2+ i ) Na+-Ca2+ exchanger Found only in excitable cells like neurons and muscle Drives Ca2+ out of cell, takes Na+ in along its concentration gradient Argued that the function contributes moreso to clearing high Ca2+ following activation, rather than at rest May work in reverse to bring in Ca2+ under conditions of low Ca2+ I
Image of page 17

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Ca2+ storage in organelles ER is the major Ca2+ storing, buffering and signaling organelle The lumen is full of Ca2+-binding proteins (calreticulin in most cells; calsequestrin in muscle) ER pumps provide a rapid means of elevating Ca2+ I , sometimes coupled to Ca2+ entry at the plasma membrane (capacitative Ca2+ entry) Ca2+ binding provides a chaperone functional that is essential for protein synthesis (i.e. synthetic enzymes require Ca2+ to make/modify new protein) Mitochondria employ an electrogenic Ca2+ channel to store Ca2+ Energy is derived from the membrane potential across the mitochondrial membrane,which reflects H+ gradients in the electron transport chain Drugs that interfere with mitochondrial H+ pumps or the electron transport chain will prevent Ca2+ uptake Mitochondrial uptake has lower potency than that for the ER BUT the capacity to store is great (protects the cell against too high Ca2+ i ) Because the ion exchange is neutral (2 H+ or 2 Na+ for 1 Ca2+), the kinetics are slower than PM or ER systems Not a source of signaling Ca2+ Nucleus and secretory granules Ca2+ stored in secretory granules can be released during times of cell stimulation and may control secretion Pores in the nuclear membrane prevent the development of Ca2+ gradients between the nucleoplasm and cytoplasm; but can also sequester Ca2+ as an extension of the ER and released Ca2+ into the nucleoplasm may regulate nucleus function
Image of page 18
Image of page 19

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Ca2+ signaling sources
Image of page 20
Image of page 21
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern