Stefan Strack, PhD


Associate Chair for Research
Professor of Pharmacology
Professor of Pathology

Contact Information

Primary Office: 2-452 Bowen Science Building
Iowa City, IA 52242
Phone: 319-384-4439

Lab: 2-400 Bowen Science Building
Iowa City, IA 52242
Phone: 319-384-4447



MS, Computer Science, State University of New York at Albany, Albany, NY
PhD, Biology, State University of New York at Albany, Albany, NY

Fellowship, Deutscher Academischer Austausch Dienst (DAAD) Fellowship, Wurzburg-Albany Exchange Program
Fellowship, Deutsche Studienstiftung for Academic Excellence
Fellowship, Teaching Fellowship, Stat University of New York at Albany, Albany, NY
Fellowship, Postdoctoral Fellowship, Morphology/Pharmacology, Pharmaceutical Manufacturers Assoc.

Education/Training Program Affiliations

Interdisciplinary Graduate Program in Molecular and Cellular Biology
Interdisciplinary Graduate Program in Neuroscience
Interdisciplinary Graduate Program in Translational Biomedicine
Medical Scientist Training Program

Research Summary

Protein phosphatase 2A in neuronal signal transduction Reversible phosphorylation of key proteins, such as ion channels and neurotransmitter-synthesizing enzymes, regulates synaptic transmission and other aspects of neuronal physiology and development. While the enzymes that add phosphates to proteins, protein kinases, have been studied extensively, much less is known about the equally important enzymes that catalyze the reverse reaction, protein phosphatases. My laboratory is interested in the roles of one of the major serine/threonine phosphatases, protein phosphatase 2A (PP2A) in normal and pathological brain function. PP2A is a diverse group of multi-subunit enzymes consisting of a constant catalytic (C) and scaffolding (A) subunit and a third variable, or regulatory (B) subunit. Regulatory subunits control enzymatic activity and substrate specificity and target PP2A holoenzymes to different parts of the cell. Research in the lab focuses on PP2A regulatory subunits that are highly expressed in brain, since they are likely to regulate specifically neuronal functions. One of these neuronal PP2A subunits, B' b is mutated in a human neurodegenerative disorder, spinocerebellar ataxia type 12 (SCA12), implying that this subunit is essential for neuronal survival. Current studies focus on structure/function analyses of PP2A holoenzymes, regulation of signal transduction cascades and neurotransmitter synthesis by PP2A, and restructuring of neuronal mitochondria by kinases and phosphatases. Select current projects: 1) Role of PP2A in nerve growth factor signaling and neurite outgrowth. Overexpression of the neuronal B' b subunit promotes differentiation of neuronal PC12 cells by stimulating the mitogen- activated protein kinase (MAPK) cascade. The B' b subunit, conversely, inhibits MAPK signaling, indicating that this important signal transduction cascade is regulated both positively and negatively by PP2A. Using RNA interference and pharmacological approaches, we are in the process of identifying the molecular targets of PP2A/B' b and B' b. 2) Regulation of mitochondrial function and neuronal survival. We have recently discovered a novel alternative splice variant of the neuronal B' b PP2A subunit that is mutated in the SCA12 disorder. The divergent N-terminus of B b2 targets PP2A to mitochondria to promote neuronal cell death by apoptosis. An outer mitochondrial cAMP-dependent protein kinase (PKA) holoenzyme opposes the death-inducing activity of PP2A/B b2. Using B b2 knockout mice and primary hippocampal cultures, we are identifying the physiological functions and molecular targets of outer mitochondrial PP2A and PKA. 3) Structure-function analysis of PP2A holoenzymes. Using site-directed mutagenesis and a variety of in vitro analyses, we are investigating how regulatory subunits interact with the A and C subunit to determine substrate specificity. The B' family of PP2A subunits are heavily phosphorylated in cells, and we are studying the effect of phosphorylation of specific residues on catalytic activity and subcellular localization. 4) Regulation of catecholamine biosynthesis by PP2A. We found that tyrosine hydroxylase (TH), the rate limiting enzyme in the synthesis of dopamine and (nor)epinephrine, is dephosphorylated and inactivated by a neuron-specific PP2A holoenzyme containing the B' b subunit. We are exploring the regulation of PP2A/B' b activity in dopaminergic neurons with the eventual goal of developing new Parkinson's disease therapies.

Selected Publications

Show All

Hatch A, Merrill R, Strack S, Strack S, Higgs H.  Actin filaments as dynamic reservoirs for Drp1 recruitment.  Mol Biol Cell.  2016 August 24. 

Gupte R, Kadunganattil S, Shepherd A, Merrill R, Planer W, Bruchas M, Strack S, Mohapatra D.  Convergent phosphomodulation of the major neuronal dendritic potassium channel Kv4.2 by pituitary adenylate cyclase-activating polypeptide.  Neuropharmacology.  2016. 101:291-308.

Ji W, Hatch A, Merrill R, Strack S, Higgs H.  Actin filaments target the oligomeric maturation of the dynamin GTPase Drp1 to mitochondrial fission sites.  Elife.  2015. 4:e11553.

Jin Z, Chung J, Mei W, Strack S, He C, Lau G, Yang J.  Regulation of nuclear-cytoplasmic shuttling and function of Family with sequence similarity 13, member A (Fam13a) by B56-containing PP2As and Akt.  Mol Biol Cell.  2015. 26(6):1160-73.

Nifoussi S, Ratcliffe N, Ornstein D, Kasof G, Strack S, Craig R.  Inhibition of protein phosphatase 2A (PP2A) prevents Mcl-1 protein dephosphorylation at the Thr-163/Ser-159 phosphodegron, dramatically reducing expression in Mcl-1-amplified lymphoma cells.  J Biol Chem.  2014. 289:21950-21959.

Merrill R, Strack S.  Mitochondria: A kinase anchoring protein 1: a signaling platform for mitochondrial form and function.  Int J Biochem Cell Biol.  2014. 48:92-96.

Slupe A, Merrill R, Flippo K, Lobas M, Houtman J, Strack S.  A calcineurin docking motif (LxVP) in dynamin-related protein 1 contributes to mitochondrial fragmentation and ischemic neuronal injury.  J Biol Chem.  2013. 288(17):12353-12365.

Strack S, Wilson T, Cribbs J.  Cyclin-dependent kinases regulate splice-specific targeting of dynamin-related protein 1 to microtubules.  J Cell Biol.  2013. 201:1037-1051.

Strack S, Cribbs J.  Allosteric modulation of Drp1 mechanoenzyme assembly and mitochondrial fission by the variable domain..  The Journal of biological chemistry.  2012 March. 287(14):10990-1001.

Baucum II A, Strack S, Colbran R.  Age-dependent targeting of protein phosphatase 1 to Ca2+/calmodulin-dependent protein kinase II by spinophilin in mouse striatum.  PLoS One.  2012. 7(2):e81554.

Date Last Modified: 06/06/2016 - 13:17:48