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Friday Evening Lecture Series
07/03/08
Porter Lecture - "From Membranes to Molecules. A Morphologist View of How Muscle Controls Calcium Movements"
Clara Franzini-Armstrong, University of Pennsylvania
Note: Thursday Lecture
Introduction by Edward D. (Ted) Salmon, University of North Carolina at Chapel Hill
 Download the video
Lecture Abstract:
The activity cycle of muscle fibers requires large movements of calcium in and out of the cytoplasm where the contractile proteins are located. An elaborate system of membranes and an unusual arrangement of ionic channels coupled to accessory proteins provide the opportunity for controlled, rapid, synchronous calcium delivery throughout the cell. Membrane invaginations called the transverse tubules distribute the initial electrical signal through the cell interior. An internal membrane system, the sarcoplasmic reticulum (SR), first described by K.R. Porter, sequesters calcium ions during relaxation. The signal for calcium release is transmitted from a voltage activated calcium channel of the T tubules to the calcium release channel of the SR. The two channels are maintained in the appropriate position and variously controlled by a large macromolecular complex involving several components of the SR that modulate the calcium release function. The system has evolved from a more primitive form in the invertebrates, that required energy consuming cycling of calcium in and out the cell, to the ultimate refinement in skeletal muscle fibers. In the latter, the two calcium channels are specifically linked to each other and influence each other’s function through a reciprocal interaction. This provides a major metabolic advantage by limiting calcium movements to the cell interior.
Clara Franzini-Armstrong is professor emerita of Cell Developmental Biology at the University of Pennsylvania Medical School, where she has taught since 1975. Her laboratory uses thin sectioning and shadowing techniques for electron microscopy to study the shape and disposition of macromolecules in striated muscle cells. Dr. Franzini received a laurea in Biological Sciences from the University of Pisa, Italy, in 1960. She was a postdoctoral fellow at the Biological Laboratories of Harvard University, under the guidance of pioneer electron microscopist Keith R. Porter, between 1961 and 1963, at the NIH with Richard Podolsky (1964) and at University College London with Professor Andrew F. Huxley (1965 to 1966). She has held academic appointments at Duke University and the University of Rochester. Currently, Dr. Franzini is an associate editor for FASEB journal and serves Advisory Board of the National Center for Macromolecular Imaging at Baylor College in Texas. She was chair of trustees for the Keith R. Porter Endowment for Cell Biology between 2002 and 2004. Dr. Franzini has won numerous awards including the 1989 KC Cole and the 2007 Founder's Awards from the Biophysical Society and an honorary M.D. from the University of Pisa in 1997. She is a member of the National Academy of Sciences and of European Academy of Sciences; and a foreign member of the Royal Society London. Dr. Franzini is a MBL visiting library researcher and a Corporation life member.
Edward D. (Ted) Salmon will introduce Dr. Franzini. Dr. Salmon is the James Larkin and Iona Mae Professor at the University of North Carolina at Chapel Hill, where he has taught since 1976. He received his Ph.D. in Biomedical Electronic Engineering in 1973 at the University of Pennsylvania under the supervision of Shinya Inoué. There he developed a miniature optical chamber for the polarizing microscope to study how hydrostatic pressure reversibly disassembles the mitotic spindle in living cells and how spindle microtubule assembly-disassembly is coupled to force generation for chromosome movement. Dr. Salmon did a post-doctoral fellowship with Raymond Stephens at Brandeis and the MBL where he studied microtubule biochemistry and mechanisms of microtubule polymerization from purified proteins in vitro. Dr. Salmon has been an instructor in the MBL Physiology Course, received a MERIT AWARD from the National Institutes of Health, given the Porter Lecture at the American Society for Cell Biology Meetings, and been awarded membership in the American Academy of Arts and Sciences.
About the Porter Lecture:
The annual Porter Lecture is held in honor of Dr. Keith Roberts Porter, a former Director of the MBL considered by many to be the "Father" of the field of cell biology. It is sponsored by the Keith R. Porter Endowment whose goal is to support communication and education in cell biology.
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